One day he was talking to Chris about how he and his dad partner would have a little girl together. He did not name anyone specific for that role. We were curious as to whether it was meant for a boy or a girl. But that is just it. It could be either one, which makes it great.
The "dad" part of the title is meant for him, but the "partner" part is, I think, genius in many ways. It could mean a female counterpart, a male counterpart, or even a counterpart who does not fit into either of those. Boyfriend or girlfriend might make an assumption that I do not think needs to be made. Wife or husband reeks of old world patriarchal roles that I have sometimes seen put one person above another in a nonsensical hierarchy that need not apply to the relationship between two people. Indeed, as often as I remember to (habits die hard), I do call what is traditionally referred to my wife as my partner instead.
Another part of it is that it escapes the expectation that this "partner" is someone who he is wedded to in any sense of the word. Just because someone wants to raise a child with a partner, does not necessarily imply any sort of romantic or monogamous relationship in any way. For example, my decision to procreate with Chris was absolutely separate from my decision to marry her. For me, it happened to be the same person, but that does not mean that it has to be.
Eventually he told us who his envisioned dad partner is. But he's five right now, and that will certainly change over time. We could attempt to tell him that the word is looking for is husband/wife/girlfriend/boyfriend/etc., but I think that might just cheapen the genius that is the term that he came up with, so I figure I will just leave well enough alone for now.