Well, I have mixed opinions so I will give you both of them.
If it a a romantic type of relationship, sometimes you can't help who you fall in love with. Yes the age difference at that time if a little big but I know 15 & 16 years olds that VERY mature for there age. Maybe that is a factor I do not know.
If it just a friend type of thing, well the 21 year old is of age to drink and I would hope that they are not imfluencing the younger one t drink also. BUT again, I dont know the circumstances. Sometimes they are up to no good and sometimes they have good intentions.
its a friendship relationship, for now. my best friend hangs out with a lot of people younger than him. i'm just worried because hes gay and i dont want him to do anything he'll regret or get in trouble for. he told me age is just a number, which is true, but in my mind, there are limitations.
Many times its because the 21 year-old is either immature or they cannot make friends their own age. Are you talking a friendship relationship or a boyfriend-girlfriend relationship? When I was 15, I had a 20 year-old boyfriend. The relationship lasted about 18 months, then I met my husband.