My brother is 15 he went into puberty chubby had moobs he lost 40 pounds now he's skinny fat he still has moobs will they go away he's 130lb ?

If he can be patient: his gynecomastia will very likely go away after he has completed all 5 Tanner Stages of puberty. "Man-boobs" or gynecomastia represent a transient increase in breast tissue that occurs to varying degrees in about 70% of normal boys during puberty. Being overweight probably made them look bigger than they actually were, because of the fatty tissue that accumulates in that area .