Source : Webster's Revised Unabridged Dictionary (1913)

Fraternal \Fra*ter"nal\, a.[F. fraternel, LL. fraternalis, fr.
   L. fraternus, fr. frater brother. See {Brother}.]
   Pf, pertaining to, or involving, brethren; becoming to
   brothers; brotherly; as, fraternal affection; a fraternal
   embrace. -- {Fra*ter"nal*ly}, adv.

         An abhorred, a cursed, a fraternal war.  --Milton.

         Fraternal love and friendship.           --Addison.

Source : WordNet®

fraternally
     adv : in a brotherly manner