To quoth the commentary (rough): ---- Remi: How dare you arrive late to our precious wedding day... you got a nerve. As punishment, You shall serve me and Flan as husband for century- no, millennia and etern... What? It was YOU who said "I can't decide", so be grateful to us for allowing you to wed both.
Flan: Since we love you and only you alone, we discussed this issue and decided to share you fairly. So we'll share this marriage and time with you for each other.
Flan: Well then... I'll have lower body, sis. Remi: Fine with me. I'm enough with this impertinent neck! ---- (In context, I think they are talking in non-visceral manner, so don't panic.)