Running in a pack is so fifth grade. Your son needs a girlfriend, not a pack of boys. He will be spending the rest of his life with his s/o, not a pack of boys. Maybe he is just more stronger and manlier than those boys, who need the pack for protection.

Please just make sure you don't make him feel like a social pariah at home for being slow to make friends or introverted.

Make sure you show him unconditional love, and let him know he is always allowed to invite friends over, offer to take him and a buddy places, etc. But then drop it.

To the PP - thank you! I really do appreciate your kind response.