Johanna I have to somewhat disagree with you, 'Sibling Rivarly" IMO knows no age, believe me it happens even in my age group and to me it is normal,it does rather depend on the situation of course,but in this particular incident I personally think it is very normal, so I really don't think Matt is abnormal or has deeper issues just because he is feeling this emotional pain, I think it is understandable and happens a lot to many people, now as to whether he comes to terms with it or not is another issue and maybe one for concern, I think his reaction is quite typical really,his feelings of jealousy, not being important to his mother anymore,(which I am only assuming this is how he feels) etc, but it is how he deals with it further down the line that remains to been seen and the deciding factor as to whether this young man has other issues.

I commend you for wanting to stand by him and help him, but as others have warned just be careful not too get in to deep, be there for him for an ear to listen., that is the best you can do really.