How do you know?

So tonight I ran into a little bit of upset while talking with my family. See, I have expressed that someday I truly believe that J and I will marry each other. We've been together for two years now. We have discussed this before and we just know that we want to be together for a long time.

Then my brother N piped up with his opinion. He claims that there are some couples that should be together for at least 5 years before they get married. And then went on to say that J and I have only technically been dating for a year and a half, since we lived together for 16 months so that's all that counts. And that the whole long distance thing and online meeting thing  doesn't really count.
I started to get upset with this, because I'm very protective of my relationship with J. I know that we started out in an unconventional way. But we're still together and our bond only gets stronger. Every person and every relationship is going to be different in some way. My relationship with J is definitely not the same as N's relationship with his girlfriend. He met her living in our hometown, they worked together, and then moved to Halifax together.
He has never been in a long distance relationship or a relationship that started out on an online dating site. So the way I see it, he's trying to "school" me on a topic he has no personal knowledge about.
I just know that I'm happy with J, and our relationship happened to start out online, but the feelings were real. The conversations were real. We still went out on dates when we visited each other. We decided to only date each other in that time we were together. By my definition, we were dating each other and that time most definitely counts.

I suppose I'm just frustrated because my family has a more traditional view of things, especially when it comes to dating. I went against the "norm" in a way by initially meeting J online. I believe I can testify for online dating and long distance relationships because I have actually experienced them.


Has anyone tried to give you advice on something they actually had no personal knowledge or experiences with? How does one really know what is real or what isn't real unless they have actually lived through the experience? 


I mentioned this conversation to J because I was upset over it, and he said that sometimes outside advice is a good thing, but in this case it's not. lol He seems to always have the right things to say :)