Missed my 19 year olds graduation

I have boy/girl twins that are both 19. My daughter has been through severe trauma since she was 5 years old. She was raped by her dad's brother for years. She has a lot of PTSD and I've spent so much time in therapy with her. She's had panic attacks. She's tried to end her life. It's been really bad. Since my daughter had always been through so much my son got put on the back burner a little. He could never have friends over because my daughter had anxiety about being around males so he started being out the house a lot and he dropped out of school when he was 16. He decided to go back and went to 19 classes and he graduated two weeks ago. I was supposed to go but my daughter ended up having one of her panic attacks and I had to comfort her and it took a while to calm her down. I ended up having to miss it and when he got home I apologized and he said it's fine and went to his room but I could tell it wasn't fine and for the last two weeks he makes certain remarks about being the forgotten child. But keeps saying he's fine. I have explained to him in the past his sister's trauma in hopes he would not only understand but I could raise a man who protects women instead of hurts them. He made a remark recently when my daughter was talking about therapy and how her therapist wants to try new stuff to deal with her PTSD and my son made a remark saying "I thought about going to therapy for my depression but then I remembered that I'm not as important." He's clearly mad at me and not fine and I don't know what to do