Hmmmm.... not sure if this is normal, however you can check with his nurses/doctor on the monthly vaccination update. Otherwise, have more outdoor play and stretch his sensory rather than just focusing on him not holding on with his hands. Its more of hand-eye coordination.
I would bring him to the beach and let him feel and experience squeezing sand. Let him squeeze sponge or even playing with dough (that you make yourself that is edible). So hand painting. Now is to increase development on his sensory. If you saying his able to hold on to either hand, continue encouraging with things that is easier for the child. Holding a toy could be tough/heavy for him.
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Momsy of 2 little sunshine