I'm a king of Kiev Rus, my vassal (duke, she) is Matrilineally married to a king of another kingdom (of Chernigov). They have a son of my dynasty.

Will he become an independent king once his father (the King of Chernigov) dies? Or he will remain my vassal, as his mom?

What can I do to ensure he becomes my vassal?

  • It's impossible to know the answer to this question without knowing the inheritance laws of both kingdoms, for example, primogeniture, gavelkind and ultimogeniture would all result in different heirs (unless there's only 1 child that was born out of either parent)
    – Oak
    Commented Mar 9, 2019 at 16:07

2 Answers 2


AFAIK, a vassal needs to be of lower rank than his liege.

That is, if the lad inherits a kingdom, that kingdom will be his primary title. He may become a vassal of whichever empire that kingdom belonged to, but he will not become your vassal by virtue of inheriting or having inherited a minor title from your domain.

In fact, it is possible that the duchy may become part of his kingdom. I've had that happen, though you might possibly be able to avert that by passing appropriate realm laws (the particulars will vary depending on game version).

If you want him to become your vassal, you have to be liege of his primary title. That is, you will need to be emperor, and make sure that the first kingdom he inherits is in your empire.

If your goal is to politically merge the kingdoms, you may want to try making the lad your heir.

  • This is only true if and only if the heir of the mother is the same as the heir of the father (which may not be due to bastards, previous marriages, different laws), and the rules of the father's kingdom allowing inheritance to go out of his kingdom.
    – Oak
    Commented Mar 10, 2019 at 14:20
  • That why I say "if the lad inherits the kingdom", you know. And what do you mean with "rules of the father's kingdom allowing inheritance to go out of his kingdom"? Which realm law says that a kingdom can not leave the kingdom, and what's that even supposed to mean? Are you referring to a hypothetical situation where the lad does not inherit the kingdom, but does inherit a lesser title from that domain? In that case, the realm law about title passing outside the domain might affect whether he inherits the title - but not the identity of his liege, which OP asks about.
    – meriton
    Commented Mar 10, 2019 at 17:03
  • De Jure laws of an Empire apply towards Kingdoms within said Empire.
    – Oak
    Commented Mar 10, 2019 at 18:26
  • So you mean that empire laws might probihit the lad from inheriting the kingdom, he will remain OP's vassal? Sure, that's why I say "if the lad inherits the kingdom".
    – meriton
    Commented Mar 10, 2019 at 18:35

The accepted answer is not 100% correct. Also the question in itself does assume a thing that is not true. As long as the child of your vassal duchess and the foreign king does not have any land on his own he is not considered your vassal, only part of your court.

Besides that, if we assume that the child is the sole heir of both, your duchess and the foreign king, the order of the deaths play a big role. Consider following:

If the foreign king dies, the child will inherit his kingdom title and instantly be either an independent king of himself or a vassal of another emperor, which was the liege of the deceased king. His mother still holds a duchy in YOUR kingdom and therefore is still your vassal. If your mother then dies, your kingdom rules play a big role. If you have rules enacted to forbid outsider to inherit realm titles (legalism 4 is needed for that rule to be enabled) the next in line will inherit, NOT the new king. Otherwise, the duchy will be plucked out of your realm and added to his kingdom.

Now, if your duchess dies first, the child will inherit her duchy, and because she was your vassal, he will be your vassal (since the title is part of your realm). When the king dies afterwards, their will be no rule which will stop this child from going independent from you (with your duchy) since his title is the same rank as yours and it is not possible for kings to have vassal kings.

My suggestion, if you really want to keep the duchy in your realm, either try to make that child your heir aswell (so you'll get both kingdoms) or try to rip the duchess of of her title and award the title to someone else.

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