I couldn't help noticing that you have only posted once, so I will take this chance to welcome you to Tamatalk! We have lots of different forums, friendly members who will help you out, and very experienced guides. It is a good idea to read the PINNED topics at the top of a forum so you know what you can and can't do.
Anyway, do you mean that you have connected two tamas, or Matchmaker has come?
If you have connected two tamas to have a baby, the girl will have twins, but one will go to the boy. You can't keep both of the twins!
And if Matchmaker comes, you can't have twins, because how would you look after them when the adult went?
If you need more help about this, anything else or Tamatalk, please PM me!