togz

Doesn't even matter if it's a boy or a girl. The older one should be told that doing things like this, and even going as far as threatening the other person, is not okay and could put him in trouble. Consent should be taught no matter what.

Very suspicious. Doing it very late, threatening the boy and you as well. I think mainly you should show the 14 year old that he can come to you at any point if he feels threatened or has something to say. Easier said than done, but at least he will know he has someone to support him. Try to explain to the older guy what kind of problems he could get into and what kind of damage he could cause by making a move or whatever on someone so young. 

keep an eye on It.

I mean, if you doing sports you also can shower together with older guys. So yeah.. just being naked whatever. But if there is any sexual meaning behind it, it's not good.

But still if you are 14/15 you can have a crush easy on an older person. And yes on that age some people know what sex is, and many also want have sex on that age, or already have done it....  (When we get older we often forget the age of our first wish to have sex)

3～4 Years age gab isn't that big. 

Also when I was that age, I loved also a guy of 18years old. (relationship did not happen, yet... I would have been mentally ready for xxx on that age ← and that differs from person to person)

Just be sure that the 14/15y person doesn't do anything against his own will. 

and if sexual things happen out of free will, be sure to give them condoms (￣▽￣;)

Juat keep an eye. Don't worry too much, but just talk calm with them about it. 

love is love, age gab or not.

What the law says isn't true for everyone.  Also max 5 year age gab, is alright in my eyes.

But still people need to know the law rules. 

good luck.