this! It's something I was thinking about. Grayson obviously struggles with impulse control (moving on, next point) so him asking this question isn't unexpected. This question is a way to learn about Dane, but it also reveals something about Grayson. He may be asking about having children because he's reflecting on his childhood and his relationship to his parents and the dynamics of wanting versus not wanting kids.

I feel like people aren't getting why Grayson is curious about the kids thing despite not even caring about having kids in the first place.
Yes the way the question is posed after Dane's thought process of alphas being able to control fertility will inadvertently lead Dane to think Grayson somehow did something when they slept together or is intent on baby trapping him, but again that was a thought inside his head that Grayson wasn't privy to. From Grayson's pov the conv went
-i won't get anyone pregnant even if i was a beta
=how
-I will get a vasectomy
=Why
-I know alphas don't worry about such things but since I have to I'll get the vasectomy
=Yes i got that but why don't you want a kid
-what do you want
=Like, hypothetically if we were to have a kid why would that bother you so much?
that's the conv from Grayson's pov lmao.
As to why Grayson is very curious, it's not just because he wants to know about the person he likes, but rather he wants to know why is Dane so intent on cutting himself off from any human connection. One night stands, strict infertility, no very close friends, living alone, diving headfirst into danger and not caring if he dies. At first, Grasyon understood that Dane is careless about his life because he has no one to live for, but now he's seeing Dane refusing to even have someone to live for and he's even more confused why would anyone want to isolate himself like this (especially because all that Grayson ever hoped for in life is finding his own person and creating an everlasting bond)