I wouldn't assume that the person doing the greater degree of wanting is the one that does the bulk of the heavey lifting and being around for the long haul.
SIL was "take it or leave it" about children. My brother wasn't he wanted them. A lot.
She still did the bulk of the heavey lifting. Had a second becuase Brother wanted 2.
He left her when she was 8.5 months pregnant.
Talking to him as it happened, I probed a little, and the arse accidentslly revealed that he knew he wanted out (replacement already lined up), but didn't want his first child to have the oh so terrible curse
of being an only child. So failed to mention to SIL he was checking out once he'd finished using her as a brood mare.
Then when the youngest was 6 weeks old he fucked off entirely and nobody saw hide nor hair of him until six months ago. The oldest is now 14.
Arses are arses, be they playing the martyred "oh I never wanted them anyway" card, or the one pushing hard for procreation.
Thank god for SIL. She may not have been the one who was so desperate for kids. But she entered into it with emphasis on the concept of them being tiny human beings, who need and benefit from a hands on, non resentful, emotional connection. So regardless of her initial "meh" stance about starting a family, when she agreed, she did so on the basis of "all in" and no fence sitting.
Just as well really considering who they got lumbered with as their father.