My baby is 5.6 years old n his weight is just 15 kg what should i give to him for weight increase??

some children do have lesser weight as compared to others, but as long as your child is otherwise energetic and healthy you should just focus on the nutrition part. make sure you give a mix of healthy foods. the mums above have already mentioned some of these options. additionally, try and get your son to play out in the sun and get exposed to fresh air and also indulge in a lot of free play outdoor.