Twin

A twin is one of two offspring produced by the same pregnancy. There are usually two types of twins: fraternal twins, which are two separate fertilized egg cells that develop into two separate children, or identical twins, which is a single fertilized egg cell that divides and develops into two identical children.

In the EMPATH: The Luckiest Smurf story series, Hefty and Handy are considered fraternal twins due to both physical differences and personalities, with Hefty being born with a heart-shaped birthmark.