fraternal

Short definition from Wiktionary

Adjective

1. 1
   Of or pertaining to a brother or brothers.
2. 2
   Of or pertaining to a fraternity.
3. 3
   Platonic or friendly.
4. 4
   Of twins or embryos, produced from two different eggs and sperm, and genetically distinct.

Noun

1. 1
   A society formed to provide mutual aid, such as insurance.
2. 2
   A fraternal twin.