Five novels and 1 short story featuring love between brothers, from the fucked up to the quite healthy, there should be something for you.
 
Plus 1 romance between cousins in extreme weather conditions and 1 dark short about a very disappointed father and his heir.
 
Ebooks included:
 
Shifters (find this in the "Intertwined Fates" file):
Not to be Borne (noncon, omegaverse, twincest, mpreg, HEA)
Always His & Always Mine (dubcon, omegaverse, twincest, mpreg, HEA)
A Light in Winter (omegaverse, cousins, HEA)
The Realm of the Impossible (royals, brothercest, genderfuck, noncon, dubcon, HEA)
 
Dark:
Incivility (mpreg, father/son, uncle/son, omegaverse)
The Weight of Duty (body modification, arranged marriage, twincest, uncle/nephew)
 
Contemporary lit:
Entwined: a love story (triplets, not a romance, HEA)