help me pls!

hi so i have this manga in my head and here’s all i remember about it

okay help me find this light novel i think it was japanese and translated and it had a title like something something little sister or something like that

but the point of the novel was like the main character loved the male lead but like no matter what she did he never loved her and always loved her little sister and like at one point he gets her little sister pregnant and then she leaves and breaks the engagement and i remember the female lead had like grayish hair on the front cover it was also made into a manga it’s like really angsty and sad and i remembered she had a knight who really loved and cared for her and at one point she gets kidnapped and treated as a sex slave and her knight comes and saves her OH OH and there’s this like wizard whose like shaped like a raven and at one point he feels bad for the sad life she lives and he helps her at one point but then she relives life over again and she never sees him again