I know that’s the case in other universes but everyone kinda assumed that in order to have had a child he must have been with a woman and for her to have given birth. It could be though because they thought Josh was a beta and male betas can’t give birth (?)
Also, unrelated, if you want a story about a female alpha and a male omega (I think - can’t remember if it was a beta or an omega but I think it’s an omega) in the love is an illusion universe there is such a couple and it has its own separate story !!

And even after this confession he still doesn’t realize he’s the father ╮( ̄▽ ̄)╭ … Josh is literally saying he’s only been with women but he has also given birth to a child… you just need to connect the dots ( ̄∇ ̄")