It sounds like he might be going through something stressful right now. There are two categories of stress. One is obviously emotional, but the other is physical. Stress on the body can happen when someone doesn't get enough sleep or doesn't eat the right foods. Of course, being stresed emotionally can also lead to not eating or sleeping well and make things worse. Try asking him if he would like to talk about anything and let him know that you're there to listen. Also, think of something you regret and appologize for it. That tends to get conversations started. Let him know you care and are just worried about him.

If he likes love and afection, hug him, it won't hurt (as long as his grip isn't to strong) It is even scientificly proven that hugs relive stress and help strengthen bonds. Also try and act nice around him and if posible try and seem even a little intererested in his favorite activities. In my family the girls are out numbered, 2-3, me and my mom verses my 2brothers and dad.