AITAH

Am I the arsehole

Am I the arsehole for being mad at my stepbrother for leaving the family and wanting to have a go at him despite my parents telling me not too because they don’t want me and my sister to be involved even though he’s my own stepbrother and my and my sister are hurt by him leaving.
8 months ago my stepbrother (13) left the family home claiming it was abusive when we can prove that it’s not and then continued to return to the home multiple times without permission to take his stuff to which my stepdad (his dad) had to baracade the door shut to prevent him from getting in.
This situation then becomes worse when he begins to continuously ringing my stepdad and asking him for silly things like the furniture from his bedroom and quite frankly when ignored by the family begins to harrass us for information about my stepdad and now he’s moved on to commenting on social media posts with things he knows are going to hosted his dad.
Me and my sister responded to this by having a go at him to which my sister got told off.
What would you do on this situation?