Is this his way of coping

So several days ago I made a post about my step sons mother passing away from a car accident. He's 15 and autistic. His mom left him on his dads door step when was 3 and never came back. He's talked to her a hand full of times but doesn't really know her. He has always called me mom and seen me as his mother. I still thought he would have more of a reaction to her passing away. He mainly just said "Oh ok" and went on with his day. He said he doesn't want to go to the funeral and me and my husband have asked several times if he's sure and he said yes so we let it be. He didn't really know her so maybe that's why. But he has been acting a bit.... Different the past few days. He's more clingy with me now. He got some race cars and Legos and stuff for Christmas and he will usually ask me or my daughter to play with him. Thats normal. But he's been wanting me to play with him non stop lately. When be has nightmares he usually likes to cuddle with my, or my husband or my daughter (his sissy). He's been saying he's having bad dreams, but I'm starting to think he isn't and just wants to cuddle, which is fine. He was supposed to go to group therapy yesterday but he had a melt down and didn't want to go. He just wanted to stay and play Legos with me. He's usually a very sweet huggy lovey kid, but he just seems to be more clingy lately. Could this have to do with his mom? How should I go about it? Should I just let this clingy phase run it's course?