On the subject of House Bolton, there's a bunch of great houses on the ropes, right? Let's talk Conservation Status.
House Baratheon -
Critically Endangered.Only one heir, Tommen, and he's not banging out Marjorie now that the faith militant is back. Plus, you know of know he's going to die terribly because he's Cersei's kid.
House Stark -
Critically Endangered. Only legitimate male heir is paralyzed. Jon's still running around, and I still have hope for Robb's letter of legitimacy. Only reason they're not on the extinct list.
House Lannister -
Near Threatened. Jamie is not banging anyone other than his sister, and I don't think that's going to make a child. Tyrion is around, but also killed his dad so not exactly sitting in the big chair at Casterly Rock. Kevan is around though. Probably a bunch of other one off relatives.
House Targaryen -
Extinct. Dany is barren and also a female. Jon is running around amid rumors of his parentage, but he'd still be a *******. I suppose Dany could legitimize him if she makes queen, but there's nothing in the story to suggest that. No other relative crawling around in the show.
House Tyrell -
Endangered. Do we know of any other male heirs other than Loras? He looks like he's about to meet his end as well. Mace could make another heir, though. And you have to think there are other Tyrells running around (similar to the Lannisters).
House Greyjoy -
Critically Endangered. Theon can't reproduce, and Yara is a chick. That leaves Euron, and he's not long for this world with Dany backing Theon/Yara's play.
House Tully -
Endangered. They are down to Edmure and his son, though Edmure is relatively young. Endangered because both Edmure and Edmure Jr. are in precarious situations.
House Frey -
Least Concern. Dude is all about
mugging stares and
making heirs.