My wife & I have an 18-year-old son. He started university in September, studying medicine. There he met this 41-year-old man - a classmate, and they became really good friends. This man has just started university now at this age because apparently he was born poor and in the first half of his life was focused on making money, but medicine is a dream of his. Son has always been an introverted, shy, socially awkward kid with little friends, but now goes out often. Honestly my wife & I are uncomfortable, and we can’t help but side eye the dude.
At age 17 I made friends with a coworker in their 40s. I found out he was into D&D and he invited me to sit in on a game. Now I’m 30 and I been playing with this group of now 50-60 year old dudes every Sunday since. Age gap isn’t strange but if your getting weird vibes maybe have a chat with your son about your concerns, but he is an adult in college now. He will likely have many connections of all ages.