Hi mommy,  all babies reach various milestones at different times,  however as a parent we can help them develop various skills... To help ur baby with this one,  u can try placing a rattle in his hand,  and gently rub his hand and open his palm,  u can repeat this so the baby slowly understands that d world can be more fun when he gets to open his palm..

Slowly she will learn. You should open it gently while massaging and also.. play with her opening fingers.. and give rattles to hold. Buy a playgym...that will help is their development...