Yarikonda Otome Game no Akuyaku Mob desu ga, Danzai wa Iya nanode Mattou ni Ikimasu

The Valdias are a seemingly normal family of nobles that no one would expect to face a future full of death and condemnation—a fate which is about to be rewritten. After a mysterious accident, former salaryman and avid gamer Hajime Kanda wakes up as their eldest child, Reid, in the world of an otome game he once fully cleared. And he knows the terrible future that awaits them all. Reid may have been a petty villain in the main story, but he's got exceptional stats that will help him grow into a total beast. The hard part will be avoiding the conflict to come, and doing that means bringing the family together again. He's just got to be sweet to his younger sister, get in his father's good graces, and cure his mother's terminal illness, of course. Should be simple enough, right? Well, Reid's determined to save his family from a dark fate, and he's going to do it by playing by the rules!

(Source: J-Novel Club)