I am a single child myself, I have three DCs, DS1 11 yo, academic, sporty, popular, interesting, easy going, then DD1 10 yo with possible Aspergers, poor working memory, borderline dyspraxia, pretty abrasive socially, anxious and low self esteem, then DD2, charming, witty, funny and clever. Middle child is terribly jealous of little sister and is quite mean to her which sadden me terribly. I don't know how to handle this as it must be really hard for middle child to literally be the black sheep of the family, but she has no right to bully her little sister like that.