Don't worry, I think it's very normal! My LO was/IS still like that. He's 8.5 months and we hadn't seen my parents for a couple of months but when they came the other weekend he cried when he saw my dad. Actually, the whole weekend if he looked at my dad he would cry! I felt so bad because he wouldn't even let him hold him without crying. He does it to my FIL too though...actually he does it with all men (except DH!) but never women?!!