Okay, here we go. This is my first post on this website, but please don't think that will reflect on the quality of the advice I am about to give.
Can a 19 year old be friends with a 14 year old? I think so, especially if the 14 year old is more mature than is usual at that age, or the 19 year old is less mature than usual. That said, pursuing a relationship with this person would probably be unwise. I know you've said that you don't want to, but I figured I'd make my opinion clear on that matter.
How, you ask, do I know that a bond can be forged between people of different ages. I am 19 years old myself, and I have a girlfriend that is 16. The age gap in this case is only 3 years, but I am sure there are people on this site that would find that inappropriate, especially since I am an adult and she is not.
In regards to sexual relations, the age of consent where we live is 16, so it wouldn't be illegal, but that is neither here nor there.
Now, this girl and I got together one and a half years ago (when I was 17 and she was 15). Her parents know me, and are just fine with me. They've even gone so far as to say that I am good for their daughter.
As for which of us is the mature/immature one... She's been through a lot of terrible things in her life. The kind of stuff that makes you grow up too fast. She's WAY more mature than the average 16 year old.
Now, why was that story relevant? The crucial difference between you and me is this: My girlfriend and I were both minors when we met. Our relationship wasn't against the law, and still isn't now. Even if it were, her parents approve of me.
My advice to you, if you are interested in him, would be to remain friends with him. In two years, he is 16, and that is the age of consent in the UK. If you really insist upon a relationship, you can try to pursue then, but his parents might forbid it, in which case you might have to wait until he is 18.
That's my opinion anyway, and I know some may not agree, but you won't be breaking any laws by following my advice, which is more than you can say if you pursue the relationship now.