I knew Shaia isn’t a real jerk and has something in mind for accepting Toneria's arranged marriage ! He just want to protect those dear to him. Of course it won’t be this simple between him and Beryl and the story would develop around how they would learn to love each other.
I’m not sure Shaia still have feelings for Theo. I agree he could have been in love when he was a child but I think at some moments he finally understood that he loved Theo like a friend or maybe a member of family but not as a lover. And I think it's a good thing, I’m not fond of love triangle.
But I’m very upset yo see that old geezer Toneria still could make trouble in the family and still plot some nasty things ! What are Luard and Juda doing for letting him messing up the lives of the child!