I don't know why but in a lot of ships & fandoms, i only ship certain charas with one gender. examples:
Homestuck - i only ship karkat with males (excluding the fact that trolls are both genders technically.) like I'm fine with male Nepeta X Karkat, but i dislike nepkat normally
Kuroko no Basuke - I don't ship kuroko with a single girl (not that there are many in the anime), but I'm fine with Male! Momoi X Kuroko or Male! Coach Riko X Kuroko
i dunno
.-.