Causes of a weak grip?

Is there a reason I have a weak grip? I've always had a weak grip since I was younger. What can cause it? It's usually when I wake up or before I go to sleep. Could it be my posture? Playing on my laptop too much? The feeling is like I can't close my hand into a fist, like I am too weak to. My mom said she had this problem so is it hereditary? My dad also mentioned something of carpal tunnel syndrome that runs in the family. Is that it?