Are they too skinny?

I have 5 friends, theyre all sisters. the oldest is 16 and 110 lbs, then are the twins Emily and Amanda, theyre both 15. They weigh well, I don't know but Carly is 13 and she weighs like, 90 lbs. The youngest Ness is like, 80 lbs. Are they too skinny?

depends on their height

You neglected to include their heights in this question, which is fairly essential in determining whether one's body-mass index is too low or too high. Weight is just one measurement of many and cannot tell all things for all people. If a person weighs 180 pounds, for instance, they would be grossly overweight at 5'0, but fairly average at 6'0.

Pay attention to their overall health, not just how much they tip the scales. That said, there doesn't seem to be anything too alarming in those numbers.

okay well, their pretty short, so the oldest, Elle is about 5'3, the twins are 5'0 and 4'8, but I don't know what they weigh. Carly is like 4'8 too. And Nessa is like,,, um... probably aroud 4'6

They are fine. I was 5'4 and 115lbs my freshman year in High School

they sound skinny