my 4 month 8 days old baby boy birth weight is 3.5 kg..now his weight is 6.7 kg...is his weight gaining normal and healthy???

A. After four months babys weight in between 6 to 9 kg is average. Certainly the baby weight will improve in the coming days. You are going to start solid / semi solid after six months which will improve the weight further to the baby. If baby is active always, baby will be healthy.