Can't extend arms completely or lift arms above head

I am taking an anatomy and physiology class, and I asked my teacher why I can't lay my arm on a table and extend it for my hand to touch the table, or lift my arms past my head. With my head straight, I can lift my arms, like the referees do for a touch down, up to about 3 or 4 inches before my ears. My father has the same problem, and so does his brother and their father. My grandfather, and my father are similarly built, with broad shoulders, broad chests, and thick forearms and about 6'3, my uncle and I are about 6'1''- 6'2'', long lengthy arms, broad shoulders and chests, and extremely skinny . My teacher says it may be fused bones, since we all have similar body builds and the same arm "deformations" I am wondering if this is a genetic mutation.