I imagine from the same place that opposite sex couples who can't get pregnant together get children: previous relationships, artificial insemination, surrogate birth-mother, adoption of non-related children, foster or adoption of relatives (nephews, nieces, etc.).
You know, this isn't exactly rocket science.
You presented a lot of options but didn’t answer the question. I know where babies come from. I have three. I asked where these children came from. But thanks.