NURSING ANM AND GNM

Detailed explanation-1: -Younger is used when there are two sisters or two persons, two pets.. Youngest is used for many, three or more, sisters., persons, pets, animals..

Detailed explanation-2: -Yes there is genetic variation and some younger siblings may be taller than the first, but the majority are not as tall as the first born. There can be many reasons for this, but most likely it is the health and nutritional status of the mother declines and depletes with every pregnancy.