I don't approve either but it seems that scene of them at the last chapter is a foreshadowing of their relationship.
If you really think about it it's not that bad, considering they're only 6-7 years apart and not 10. Casel, Reia, and Ladius just look a lot older than most kids their age (18-19 yrs) because of how they dress and how they behave, and also the art.
It's quite surprising they got married that young when their parents don't look a day older than 30. They're too young, I tell you! At least let them reach 20 before getting married.
I didn't really want to see their children living out their love loves, I wanted more on the parents . That's what disappointed me the most.
Hmmmmmm I really hope the lil sister doesn't marry the friend, it feels wrong on all levels. There's a what? an almost 10 year gap? Nope not approved