fraternal

Fraternal is an adjective meaning relating to brothers or to brotherhood. It derives from the Latin frater, meaning "brother," and is used to describe kinship, bonds, or organizations founded on mutual fellowship.

In biology, fraternal, or dizygotic, twins result from two separate eggs fertilized by two separate sperm. They are genetically similar to ordinary siblings and can be the same or different sexes; they differ from identical (monozygotic) twins, who arise from a single zygote.

In social and institutional contexts, fraternal describes groups organized around friendship, mutual aid, or shared interests, such as fraternities, sororities, and fraternal orders. These organizations may emphasize mentorship, philanthropy, scholarship, or professional networking.

In moral or religious language, fraternal affection denotes brotherly kindness and solidarity toward others, including humanitarian or charitable actions labeled as fraternal charity.

The noun corresponding to the adjective is fraternity, referring to a brotherhood or a society; 'fraternal' is the descriptive form used for related concepts.