Well even though your male sims 3 sims will not have little green babies. With the help of some mods that allow same sex pregnancy they can have babies. However they have no clothes and will end as floating heads. Well here are a few outfits that work if men even find themselves with child
You can use them as normal clothes to.
some base game outfits with a pregnancy forf added to them. again done by CmarNYC
[You must be registered and logged in to see this link.]

And something for teen boys in a unique situation. Also by CmarNYC
[You must be registered and logged in to see this link.]

A few more outfits for teens here by ......I am not sure if their name since it is anlother launage. But I think its Myos
[You must be registered and logged in to see this link.]