There is a very popular computer game called Crusader Kings II. As far as I know, it is the game that tries the hardest to represent a feudal society and the liege/vassals relations (although, obviously, it takes several liberties).
In it you have the option to propose a "matrilineal marriage" that is, all the children born from that marriage are to be considered part of the mother's dynasty instead of the father's. This option is mainly used to prevent family names from disappearing due to the lack of male descendents, or in some cases, to maintain a certain family as the head of a monarchy.
Is this just a gameplay mechanic or does this have some historical accuracy?
Note: A very similar question has been posted here nine months ago, but it recieved no answers.
You know, I can't think of a single ruler in Europe where this happened the way it does in game. However, there is an alternative method that I was always disappointed was not in the game, which is the creation of a new line, descendant from the previous one. The most famous example of this is the House of Lorraine, also known as the House of Hapsburg-Lorraine. This was the marriage of future Archduchess Maria Theresa of the house Hapsburg to Francis of the House of Lorraine. Their descendants thus became members of the House of Hapsburg-Lorraine. However, this was an exceptional case because of the stature of the former. The most common method to retain the house's control over a certain principality was by keeping marriage in house. This was the case with Isabella of Castile, Joanna I and II of Naples, and a few others.
In reality, however, the majority of women who inherited the thrones of their dominions saw their lines die out in short order. For the most part, very few holdings would see a woman get to the throne unless there was literally no males left in the direct lineage for their houses. And thus, unless you could keep it relatively in the family by marrying someone with no real claim to the throne but still part of your house, the line's control over that realm would end.
It's difficult to prove a negative but certainly I've seen nothing in my reading to suggest that such marriages happened, never mind being common. Given that such marriages were exceptional, you would expect one or two cases to be well known examples. So I strongly suspect that it's a gameplay mechanic.
But it's certainly a necessary one. In CKII the objective is to maintain a line of direct inheritance over 3-4 centuries. The reality is that simply accomplishing that was beyond most medieval families. Low life expectancy, high infant mortality and the inherent violence of medieval life meant that most aristocratic houses were doing well to create an unbroken line of succession over the course of a century. According to Edouard Perroy (quoted in Barber's The Two Cities) a typical medieval French noble family was unlikely to maintain a direct line in inheritance for more than three generations (with even indirect succession rarely lasting more than six).
This seems to have been the case across Europe. Bartlett (The Making of Europe) gives examples, including that "of the 16 families of free lesser nobility in 12th C Osnabruck only six survived to 1300; and of 70 knightly families enfeoffed 1125-50 in Eichstatt, 30 died out before 1220". I've also seen references elsewhere to the diminishing odds inherent in the sheer genetic lottery but annoyingly I can't recall the specifics or the relevant work.
All of which explains, in part, the prestige accorded to those successful houses – most obviously Capet of France – who managed to regularly produce male heirs over successive generations. It also shows why some game mechanic was needed in CKII to allow the player to maintain a direct line. Otherwise most players would experience a very short game.