I have two sons 6 and 16 and a stepson who's 10 (as well as a 5 year old stepdaughter. (she gets along well with everyone). However my ten year old stepson never warmed up to me, he seemd kind of scared,of me, so I try to be sensitive to his needs and kind, I don't try to discipline him. He seems sad and withdrawn after his mothers divorce. My eldest son has tried really hard to befriend him. He have him his room, tries to get him to laugh or play video games , sports etc. but my step son yells at him that he's not his real brother. The only time he was semi-thankful was when my son protected him from a bully. My son stopped trying and gave him space, but for some reason after 6 months he started trying really hard to befriend his stepbrother again and is still trying.

It's been well over a year and me stepson is only close to his biological mom and sister.
Can I do anything to make him happier and more comfortable. His school therapist says he is not depressed and he gets good grades, but he seems pretty sad to me, always holed up in his room.
Any advice would be appreciated.
Tom