Mc is recruited by a noble to act as the noble's lost younger brother because they look similar. The lost brother is dating the crown(?) prince, so mc has to act like the prince's lover too. The lost brother (mc, now) is a 'weak' night and often bullied by other knight despite his noble position (I forgot if he is a legitimate son or not). At some point there's some kind of incest since the brother is sleeping with mc..
When will they stop fucking and start parenting