I can see how they could be in love (how sweet!), but it would be pretty silly for them to have babies, considering it would be biologically impossible in the real world ;oP Maybe they can adopt?
I've never heard of anyone's same sex tamagotchis having children, but IF they did I imagine it would be the exact same as two opposite-sex tamagotchis - i.e. each parent would end up with one baby. Connections are not programmed to allow you to raise two baby characters at the same time on the same unit.