My 14 year old (year 10) son doesn't have any friends except one who is a home-ed child. They see each other maybe twice a month, and mostly only if I prompt him to do so or arrange something with the friend's mum.
He seems generally happy enough in life, he doesn't love school but I don't believe he's being bullied or anything. He used to have friends at junior school. At senior school he seemed to grow apart from the people he knew (some of his junior friends went to different secondaries and have eventually lost touch despite me trying to help him stay in touch). For a while he was friends with a group of girls at school but now doesn't really seem to still be friends with them either. At lunchtimes/break he just reads or does his homework. I think he does interact with other kids but he's not actually friends with them.
He's not interested in sport and finds a lot of the boys his age a bit idiotic. He's not remotely interested in vaping/drinking which lots of them are. He's shown no signs of any romantic interest in anyone male or female.
He goes to extra curricular activities three days a week after school and chats to other kids there but there's nobody he'd count as a friend. He can interact fine with people, eg we had an exchange student to stay, they got on fine, played games together etc and he isn't cripplingly shy or anything.
At weekends he has tutoring, ocassionally plays roleplay games with a group including his home-ed friend, otherwise he plays computer games, guitar, draws, reads, watches telly, or we do stuff as a family (two older teen sisters).
I'm not sure he feels a great gap in his life and his time always seems filled up, but I worry about him not having friends. I don't think there's much I can do except encourage him to see his one friend and hope maybe he'll find someone he gels with when he goes to 6th form college.