Where’d they get the children from?
How about the real meaning of “been together”? Are they just roommates? Is or was their relationship sexually exclusive just like the expectation of monogamy?
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.
Pooped ‘em out ?