Incest Tier list:
God tier:
Lil Bro x Big Sis
Big bro x Lil Sis
Normal Tier:
Mom x Son
Mom x daughter
SisxSis
Twincest
Shit tier:
BroxBro
DadxSon
All relationships can be converted to areas further on the relationship tree, for example Older female cousin x Younger male cousin is still god tier.