Why dont I grow if my dads so tall?

I turned 15 this decemeber that ped and im only 5'6.5". Im shorter than all my friends. They all make fun of me calling me a shorty and asking me why im so short if my dads 6'2". My sister even a half inch taller than me. My whole families in the 6 foots. WHy dont I grow. If you think i can still get to 6 foot, be relistic and tell be how exactly. Tell me how much you think im going to grow each year.(MY DAD GREW UNTIL HE WAS 22) 1 funny thing (MY COUSIN WHO LIVES WITH ME IS 6'0.5" AND HIS DAD IS like 5'6", HOW IS HE SO TALL IF HIS DAD IS SO SHORT AND WHY AM I SO SHORT IF MY DAD IS SO TALL. Literally why dont i grow. I drink like 5 gles of milk and eat my vegatables and trust me, I eat a lot of meat for protein.