Good day.my son is thin. i want him to eat and eat to gain his weight.so seldom to eat.what is the best vitamins for him to take?thanks

None, Real Food Best: Vitamins are all single molecule cofactors. The human genome has not maintained instructions for every single step to manufacture; typically missing only a single step. But why should this be maintained when vitamins are so plentiful in almost all non-processed foods in nature? Vitamin deficiencies 1st world countries (except D3) very rare; it is big business to promote/sell reprocessed food waste

Hard to say: You have not provided an age, weight or other factors that would help in formulating an answer. Kids slow their growth from the 1st to 3rd year dropping from 10 inches & 14 lb/yr to 3 inches & 4 lb/yr.They remain at that slow rate of growth until the pre-teen years. I expect a toddler /child to eat well 4-5 days a month, and nibble the rest.Most don't benefit from vitamins unless deficient.