Matthew (which on balance is the strongest of the two for reasons passim) hints that 'relations' happened after Jesus was born. So it hints that there could have been biological children.
I do find it quite an interesting question to post and ponder because it did facilitate the unraveling of my own faith. Not the last piece; I'd already settled on accepting adoptionism some time before. Part of that was because yes, on balance she would have had children. Yes, from what we know about contemporary Jewish betrothal, she would have been of an age that we today would rightfully baulk at. And lastly, I do not believe she could consent. Or if she did, that it was valid. Not a matter of age, but as a matter of power. And I didn't think that was how god would 'move' (particularly such a gendered move)
So blep. Fun fact for you all.
There's been some really interesting discourse about exactly this situation with the Annunciation. I admittedly am very sympathetic to the belief that Mary's consent was present and was valid, but it's an important point to discuss in Christianity.
I think certainly there should be room for discussion about it, as much as there's a bit of discomfort around it.
My own view is that not only was she was not in a position to give valid consent, no one would be. I think there's an expression of
maleness in the ask/act too. And a certain type of maleness that as a believer I started to have discomfort in (tldr; the end product of procreation as a signifier of a 'beyond doubt' expression of maleness divorced even from the sexual act)
I just don't think a deity would appeal to such base appropriation of contemporary Galilean 'male gaze' norms. Particularly given Jesus' rejection/inversion of the same.