Daughter had unprotected sex with 2 guys 10 days apart. who is the likely father?

Not enough data to know. It depends on when she produced a fertile egg that was available which is unknown in this case. A NIPPs test done on a sample of mothers blood can detect circulating non cell material from the fetus after 8-10 weeks. This test is accepted by a court as establishing paternity.

More information would be needed such as when she had intercourse during her cycle. In any event a paternity test might be necessary. To prevent pregnancies and STDs your daughter should insist on appropriate contraception.