How old is axel from Kingdom Hearts

Axel is 16 in birth by sleep{Doesnt apper in B.B.S.}

By the time Roxas was made that was 5 years later cause ventus has been in Castle Obllvion since then

16+5=21

then roxas was created a few seconds after roxas was created}{From remains of ventus's memory's}

Axel is 21 years old