Summarize this article in one sentence.
If your guy’s in his teens or early 20s, his brain is still developing. This could make him do or say “stupid” things without thinking first. Issues like overparenting, youth obsession, and tough economic times can cause older guys to act immature, too. Understand and forgive him when he says he doesn’t mean to make you feel left out. He’s likely telling the truth. Everyone feels like they have to do what their mates are doing.  If the gang wants to play video games, don’t get disappointed if he doesn’t feel like cuddling with you. Put yourself in his shoes, and imagine how you’d feel if he told you not to join in with your mates. His mates have been there longer than you have. Never make him choose between you and them. Show him the same respect you’d expect him to show you with your own mates. Sabotage shows a lack of trust and respect. Avoid calling or texting when you know everyone’s getting together for the weekly football match. Don’t invent emergencies to get him to leave them for you. Never delete texts from his mates. You don’t have to pretend to like anyone, but you shouldn’t start a war, either. If you encounter a mate you don’t like, a simple “Hey, how’s it going?” will do. If they walk up to him when you’re together, acknowledge them, finish your conversation, and politely excuse yourself. Tell him the truth about your feelings, but reassure him that you understand the value of friendship. Use this as an opportunity to hang out with your own mates. Chances are, he’ll be okay with your decision.

Summary:
Step into his shoes. Accept his need to fit in. Don't make him choose. Don’t try to sabotage their friendship. Act civil to the mates you don’t like. Give him some space.