2 alphas can still have kids .. their was manga where 2 alphas and he got pregnant

not in this one

well all of them are different

Authors often add their own Omegaverse rules in their work. Not exactly sure about this one, but two male alphas generally can't have children. If it were between an alpha woman and alpha male, it should (usually) be possible. But again, depends on the author as some work outright only have omegas as the only sex that can give birth.