For those of you who play medieval/tribal/fantasy/what-have-you neighborhoods ruled by a King or Lord or some other sort of hereditary sovereign, how do you handle issues of succession when the sovereign dies (or abdicates, if you allow such things)? Do you go with traditional male primogeniture? Absolute primogeniture? A kingsmoot to choose the next monarch? What if the heir isn't an adult yet, but still a teen? Do they still get to rule? What about a child, toddler, or infant? Etc., etc...

And what does being the sovereign mean for the Sim who it falls to? Do they just get to live a life of luxury while a regent or council actually runs things? Or are they more likely to have to take a hand in running their kingdom?

Let me first admit that I don't play such a hood.

I do have some ideas for the king or queen though!

In my hood, they will run community lots as owned businesses, to start with. Botanical gardens, royal museums and art galleries, etc.
Depending on how good/evil the sovereign is, admission fees could be set to low or high.
Some form of tax will be suitable, I think - which can achieved by using a mod (I would probably stick to a very simple one, like Pescado's money order) - or perhaps just using the family funds cheat.
I will simply make the eldest child the heir.
I will have the sovereign live in a castle with some other sims, the spouse(s) and children may have their own castle(s) in case of too many sims on one lot to handle.
In the sovereign's home, I will move in some sims to form an advisory council for the sovereign - they would be elders, because they are wise, like a retired general and a retired mayor. I think the sovereign may also be entitled to having a personal doctor in the house, but a scientist with his career reward may be better, since he can make medicine if the sovereign is sick.
A good sovereign may decide to build a hospital or schools or research facilities. The evil one may go for gambling lots.
The sovereign will go to the vacation destinations often - with his council members (diplomacy) or with his family (vacation)
Of course, he will entertain, so there will be fancy parties in his castle too.

Well... in Kulo Seeri, which - as I've mentioned before - is a tribal hunter-gatherer culture, and home to a lot of my complicated worldbuilding ideas, here's one of my standard rambly posts on how it works:

Kulo Seeri is matriarchal. It's ruled by a headwoman, who must be descended from my founder purely through the female line - that means that the headwoman is always of the zan-Avira clan, since only they can claim that distinction today. She also has to be born with a twin, since the zan-Avira clan nearly always produces twins, and single births in the clan are seen as unlucky. Sims who qualify use the last name mi-Avira, rather than zan-Avira, to show that they're eligible to lead the tribe. I am considering allowing ruling matriarchs of other clans to use the mi- prefix.

There was never a direct mother-to-daughter succession in Kulo Seeri; the culture reveres elders for their wisdom and experience. Traditionally, the role of headwoman always fell to the eldest mi-Avira woman in Kulo Seeri. Etan, the current headwoman, has altered that in the code of law she's just finished writing. Now, the way it works is that matriarchs of other clans get to choose their successors from among the women of their clan. They can change their mind at any time while they live, which will likely lead to rivalry between sisters and cousins. When the headwoman dies (or becomes unfit to rule - it happened to Etan's mother Kitira and aunt Kenda, more on this later) then the matriarchs of the other clans get together to decide which of the other adult mi-Aviras will be the next headwoman. (Note: "adult" in Kulo Seeri includes teens, but only those who have succeeded in the rites of passage.) If there are no adult mi-Aviras, it defaults to the eldest daughter of the bloodline, and the matriarchs are instead choosing a regent from among their own ranks. (And no, they can't nominate themselves.) If there are no mi-Aviras period, well, I don't know yet because this has never happened so far. But it probably won't be pretty.

Responsibilities of the headwoman include ensuring that everyone has enough food and water (but that they're not taking more than they need), hosting regular gatherings of the clan matriarchs, settling disputes between members of the tribe, and handing out punishments for those who break the tribe's laws and customs. She's also expected to not lounge around in her tents all day, but instead take an active role in the lives of her people. At the moment, the only way that a headwoman can be unseated is if she breaks one of the Seven Unnatural Evils of her own volition, or becomes any sort of undead - willingly or not. (The second bit is what happened to Kitira and Kenda - vampire and zombie respectively.) She can step down in favour of another mi-Avira at any time. I am currently working on a Clan Honour Points system, based on the values of Kulo Seeri culture, that will help me see who the other power player clans are in the tribe, and it's looking like the only serious rival to Etan is the chief elder, Serendipity zan-Carmela. Half the clans actually have negative honour; I haven't decided what that means for them yet.

I think I've covered everything now, so I'll leave off rambling here.

I haven't done a full neighbourhood ruled in this style, but I typically have a line of succession.

In Huntsville, it was patriarchal. Matt Hunt's eldest son Aaron became the heir. Then his son, Andrew, whom he and his wife Alicia tried for years to conceive (they had 3 girls and a miscarriage first).
Andrew then died in a tragic spaghetti fire days before finishing university and marrying his true love, Hannah.
Quinten, Aaron's younger brother, had been acting as regent, so could not become patriarch. His oldest son, Ryan, refused to take on the role, so it fell to the younger brother, Cole. Cole and Andrew had been very close, and when his wife Aaricia, drown because she went swimming while very pregnant, the sorrow of his losses and the pain Hannah equally felt had the two of them end up marrying.
They had 6 children, the eldest, Matthew Hunt, is now the heir.
When the game got locked on a broken computer, the one concern was that Ryan had ended up getting married and having a child - luckily a girl. But there was always a chance for the succession to get completely screwed up.

I have in my mind the idea of creating a fantasy hood in which there would be heredatary titles - but since I'm loving my current one it may take forever before I make it real.
In my idea, the leader would choose a heir from their children (if any) depending on their own personality.
So a Family Sim would prefer a heir who has many children of his own. A Popularity Sim would prefer the child whom has a bigger long-term relationship score. A Fortune Sim would want a rich heir. And so on.
For that reason, Fortune teenagers would always choose as a secondary aspiration whatever the main aspiration of their parents are, so they might align with such interests and increase their probabilities to inherit the title.

My attempts at creating a full Medieval/Fantasy hood always fail at the amounts of CC it needs and how long the loading times get due to that (ain't got enough patience or freetime for 30 minutes loading time)

But in my current hood the various "Pseudo Aristocratic" families (like the Goths and the Landgraabs) practice patriarchal primogeniture when it comes to being the "Head" of the family clan and to inheriting the family's manor. That means usually the oldest son of the current Family Patriarch inherits the title and manor, unless the Patriarch doesn't have any sons, then his younger brothers, nephews etc inherit, the next closes male with the same family name. Only if a family doesn't have any male members at all anymore, then the daughters would inherit.
That's for the Goths, the Landgraabs, the Wolffs and the Crumplebottoms, anyway. And it was the supposed to be the case with the Altos but they didn't last long and there was a lot of infighting and usurping. And well, those families are meant to be antiquated.

If I manage to create an Alien Dynasty, then it will actually be Matriarchal, the Terranos might turn into that. I also might have a human Martriarchal Dynasty in the making, Darryl Danders took Ellen Frost's family name when he married her, so if they manage to build a dynasty it will be Martriarchal.

I like having family names being passed down either in the female or the male line, kind of gives rules for when a family name can be passed down and heightens the possibility of family names becoming extinct.

The humans of Riverblossom Hills favour male primogeniture. The eldest son is the heir to the throne, while younger sons are sent out to conquer new provinces, and King's Daughters may act as regents where required. If a prince or lesser nobleman dies without a son, the king will decide who should succeed him. If the king dies without a son, his eldest daughter succeeds him and takes the title of king. If a king has no children, the throne may go to his sister (unless he has a younger brother who is not yet adult and therefore has not yet taken command of his own principality). If it ever comes to pass that a king should die leaving no children and having no sisters, there will probably be civil war as the princes fight over which of them will establish a new Royal House.

If the heir to the throne is a minor, an older sister or aunt will act as regent; if he has neither, his mother will become regent, supported by a Plantsim Guardian. If the heir to a principality or dukedom is a minor and has no older sisters or aunts, the king will appoint a regent, who may be the boy's mother, a more distant relative, or simply a favourite of the king. During the regency, income from taxation will go to the regent rather than to the minor, though the regent is required to live with the minor and pay all his household expenses.

The Plantsims are matriarchal and place greater emphasis on age, so when the Grand Matriarch dies, the title will pass to the eldest Matriarch. Care of the deceased Grand Matriarch's Garden (or of the Garden of any deceased Matriarch) will pass to the eldest female Plantsim who does not yet have a Garden of her own, regardless of whether she is the deceased's daughter. If there was no female available anywhere to become Matriarch of an established Garden, the eldest male Plantsim resident in that Garden would temporarily become Head Gardener, until a female was available; he would have the same reproduction responsibilities as a Matriarch and would attend the Matriarch's Council, but he could not become Grand Matriarch.

There is no monarchy in my Isles. Only an almighty grilled cheese god that plays favoritism.

My medieval-type hood is a matriarchy so the eldest daughter becomes the monarch. If there are no female children, then the eldest son does. I haven't played in a while, so I can't recall any further rules I had in place.

Today's Veronaville is possibly best known for its avant garde fashion houses, and its vibrant nightlife. Or as a centre of gay culture. It's certainly a modern progressive place, working hard to rid itself of the last vestiges of its old reputation as a place of semi-criminal feuding. It has become a thoroughly desirable place to live.

But the town has a long and distinguished history, with roots going right back to the middle ages (though most of the old buildings standing to day should be dated more correctly to the renaissance or early modern period, rather than the medieval). Indeed the town's current pre-eminence in the world of fashion has its origin in centuries of experience in textiles going right back to its time as a centre of the medieval wool trade. Wealthy clothier merchants once exchanged bills on the site of Veronaville Market. (The current Market building dates from the late 16th century, and its upper storeys were once used as a warehouse for wool and other local produce.)

Constitutionally Veronaville is a Grand Duchy, having as its head not a Grand Duke, but (usually) a Grand Duchess. The position of grand Duchess falls to the head of the famously matrilineal Capp family, and today that person is none other than young Juliette Capp. The rule of succession is one of female primogeniture, essentially the mirror image of that which until very recently applied in the British royal family. Males can succeed but younger sisters and their children take precedence. So Tybalt could have been Grand Duke, had his younger sisters Juliette and Hermia not been born. He is currently third in line for succession. But when Juliette and then Hermia get married and have children, their daughters, and indeed sons, will take precedence over him, so he is very unlikely ever to become Grand Duke. (It should however perhaps be noted that, despite a rule of succession favouring males, for most of the time that the United States of America has been independent, the British head of state has in fact been female!)

Veronaville today is a constitutional democracy so the role of the Grand Duchess is largely symbolic. I have to admit that I don't fully understand Veronaville's constitution, since it appears to have Councillors, Assemblypersons, Senators and a Mayor, which seems rather a lot of politicians for what is essentially a city state. There may even be some sort of house of representatives too. Perhaps Juliette will help me to understand it.

Juliette is now coming into her majority, and is starting to take over the duties of Grand Duchess from her grandfather Consort, who has been acting as Regent during her childhood. Consort's rule has not always been popular, but Juliette is an intelligent modern girl, and she has a good rapport with the townspeople, especially the teenagers, whom she mixes with freely. Veronaville's population is predominantly young, and Juliette, who many believe is wise beyond her years, is well attuned to the aspirations of her people. All told, Veronavillians are hopefully looking forward with some confidence to a new age of enlightenment and prosperity under her capable rule.