not sure if its otome, but its similar to 'actually, I was the real one' where the princess mc went back in time and she was actually a fake princess (she had brown hair yellow(?) eyes). she was the child of a commoner whose mother put her there to pretend she was the princess. the commoner mother, meanwhile, looked after the real princess (white blonde hair). the mc's real dad was the head magician of the magic tower and she had dozens of blood siblings. she tries to avoid death by introducing the real princess herself (the real one is a bitch)
its very popular but I cant remember its name T.T