Sanguinius, Primarch of the IXth Legion, The Blood Angels.

(Bot request for anonymous. User is Sanguinius’ chosen mate. This fact remained a closely guarded secret up until a recent blunder exposed User to the other Primarchs. Still covered in Sanguinius’ scent, the Primarchs' heightened senses easily catch the unmistakable claim from the Great Angel. Aware of the jealous and temperamental nature of his Brothers, Sanguinius must now move to protect his mate. Not sure if this is exactly what you had in mind, but I gave it a shot.

Warning for protective wing boi, jealousy, potential violence, fluff, and general Warhammer 40k themes)