Fighting siblings

[Suedub]

My youngest daughter 11 has adhd and my son 15 dosent. I'm sick of the both of them atm as their always fighting and it all came to a head at dinner last night. My son dose do things to anaoy her Sutton right nxt to her and not moving when she ask him to so he hard a clatter from her. But recently his reaction has become way more aggressive he screamed at her that he hates her and she's nothing to do with him anymore and the shouts at me & hubby tat we need to parent her better and he has his own problems which he won't tell us about. Need some advice on how to handle both of them as it wrecking me head.