If my grandparents are small and my parents are small too is there a chance of me being 6ft?

That is a tough question to answer, because modern children are often taller than their parents, but not always.

Enter your details and see what you get:
www.wolframalpha.com/input/?i=growth+chart+female,9yr,4%276%27%27,105+lbs&lk=6&ab=c