What noun is a girl and boy?

This is a bit of a tricky question! There isn't one noun that specifically means "girl and boy". Here are some ways to think about it:

* "Children" is the most common and general term to use when referring to both girls and boys.

* "Siblings" works if you're talking about a brother and sister.

* "Twins" could work if they are a boy and a girl.

* "Couple" might be used if they are a romantic pair.

Ultimately, the best noun depends on the specific context of your sentence!