Is it possible for a guy to be shorter then his sister or mother? I never seen it or at least I seen same height is it biology or something?

Yea if he is a gay fàggot

Normally you should be somewhere between your mother and father but there is the possibility you can be outwith this depending on a number of factors.

Of course it is. He has only half his father's genes and half his mother's, and there's no guarantee as to which halves those are

English not first language so sorry if it's bad. Yes it's possible but on average a guy will tend to be taller than his mother or sister. If a guy is shoorter than it could simply be unlucky genetics or bad diet that stunted groowth.

my ex roommate was a 5'5 guy that barely weighed over 125 pounds and his mom was overweight and an inch taller than him.

he also has a sister that looks bigger than him as well

Yes, it is possible! When talking about genetics related to height, there is a range of possibilities of what a child's height could be according to the height of their parents. If Mom is 5'2 and Dad is 5'6, the range of possibilities would be around 5'0-5'11. So yes, it is very possible, and gender doesn't affect the outcome.