Hence why the father will be on a lookout for a potential "fated maiden" for his son.
Also, the "genius" doesn't have to fall in love romantically. They just need to FEEL something, preferably love. The previous ones doesn't really feel anything, not even to their own parents. Cecil does respect his father from childhood, but being with Bertia actually helps him to feel and appreciate familial love for his parents.
In any case, Anzat doesn't have to love Anikis romantically. He just wants her to be with him forever because he thinks of her as his "fated maiden". In the first place, Anzat grew up "feeling" love, because he was exposed to his unpredictable mother his whole life, so he has a slightly different view of emotions compared to Cecil's childhood.
So no, he probably doesn't feel love romantically for Anikis. But I wouldn't put it past him to never let Anikis get married ever, so if nothing is done, in the future, he might actually "marry" her just to keep her by his side, wether or not feels anything romantically or sexually for her. I wish there's a sequel of him meeting an equally interesting woman in the future so our Anikis can get to meet her dream guy LoL
Idk if I read this wrong but there's no way we're ignoring the siblings
I hope I misinterpreted this wrong ab their sibling love