Is polygamy allowed in the Albedo universe? (pg. 360)
I'm thinking that the situation is more about Dea Kho (hope I got the name right) not being able to have children, and has decided a family with Karema will be sufficient to fill that gap in their lives. Looks like polygamy is acceptable to me. See page 207 - Itzak gets lucky by "answering" a contract. There seems to be contracts for mates put out all the time. I would suggest that relationships are far more open in the Albedo universe than ours.
The system doesn't have an issue with any number of combinations, only that they not be abusive/exploitive.
I imagine that it must be a variation of the Islamic system, where a man can have several wives, with the only difference here that it can be a man or a woman, and they can be from different or the same sex, I think.
With regard to Dea and the Hitzoks, how could Dea have children with Onni, if she is a Vulpine and he is a Canine? I understand that foxes are related to wolves and dogs, but I've never heard of a dog or wolf who mates with a fox, as far as I understand. (And before anyone asks, in the Albedo universe people of different species can't bear children with each other)
Dea can't and wouldn't want to, if you more carefully read the page. That's what Karena is going to do, be the mother in the trio. The various populations can't really interbreed well, they are not different species in the normal sense, as they are all genetic constructs that look like different species, but the morphological genetic sub-sets preclude mixing. However, surrogancy is very simple and even parthogenic repro is possible.
That's parthenogenic reproduction
interesting discussion either way you look at it :)
Even here, you don't need a 3 way marriage. Just a couple and a live in friend. With benefits. There isn't much protection for #3, but it beats living alone.