stuff happens here

Do I have to put some stuff on stage?

They are major characters, if not the main one, and they will marry and have children before they take a significant part in the events.  So, how to allude?  Wooing, wedding, offspring?  Or just some?  How about the assignment to a team -- which will be significant only later.  When it will be very significant.

This would be backstory except that the main character's story started earlier.