Thats someone just evil and genuine disgusting about tropes like 'wanting to keep your blood pure' or 'marrying someone to have children with that or this or their power' or 'marry into the family to streght the lineage'
Kinda reminds me of that Marriage Law bashing idea from Harry Potter that, when purebloods finally get that they are probally having more squibs and weak magic because of the sheer incest, they would forced muggleborns to marry their children so they won't lose their magic
Or Naruto fics with Clan Restoration Act that are a weird harem fetish instead of the disgusting nightmare it should be. Some even has the Uzumaki girls (Karin, Tayuya) as nothing more than Naruto's fangirls and helper without a opinion of their own, ignoring they are as much part of the Uzumaki clan and bloodline, just to be a broodmare.
Been reading a few works with Troy and Illiad lately, and, while not much as for children as its for the spouse itself, taking a 'war prize trophy bride' fits here too.
Or the old trope of a poweful female protagonist having people wanting to marry her to their sons? Or themselves? Usually powerful creepy old man
I imagine if something like what happened in Maquia: When the Promised Flower Blooms could happen in Numenor with the Elves
Mind you its a interessating idea and I actually like this trope when its acknowledged as evil