My best friend had sex with a girl, they are both 13?

They both need to talk to an adult they trust about this, they're both underage and 13  years old is too young to be having sex, it's not too young to get pregnant though.

It's sad when someone that age doesn't realize that casual sex is something they will regret, they should wait until they're older and have met someone really special because at 13 years old their feelings will change multiple times in the next five years.

If you have any influence on them tell them to wait they're playing with fire.

  Maybe he
  was upset that u wouldn't preserve your virginity till you get married. He
  was probably really upset FOR you.


  Maybe he didn't expect he best
  friend to do something like this at 13.


  In my case he does have a little
  right to ignore u since he's angry at you.


  I mean, u could get into trouble
  for having sex with another underaged person.

So yeah... That's super young. You might want to tell someone about it, an adult. If you're anxious or annoyed or even jealous just make sure you don't spread stupid rumours - just talk to an adult or someone who you trust.