My son aly had 23kg wight 131cm hight and his basketball captain told me that he should gain 5kg to be in the normal wight what you advise me to do?

Protein before fat: Are u trying to gain weight for strength, for health? I would favor proteins over fat. This should be coupled with increased exercie to bulk-up your muscles. This will make you bigger and stronger but healthier thean just eating fat. Most likely you will consume sufficient fat in the process of increasing your protein. Breads, rice , legumes, soy all high in protein. If not vegetarian, meat.

Lots of factors...: What's your pediatrician advise? How old is your son and what's his anticipated height? What other medical problems exist, e.g. diabetes? How much does he want to play on this basketball team?