Oh girl, I saw myself in your post. Here's my life story.
I fell madly in love with Jose when I was 15. We didn't know each other, and I made sure that he knew I was interested. As the years went by, we were still not dating, though we became friends. Since I was white and he was mexican, he told my friend that he wouldn't date me, because I didn't speak spanish...where I could communicate with his family. I knew he liked me if that was his only reasoning. But I stood by and watched as he dated other girls. It KILLED me.
When I was 18, Mark asked me out. I was head over heals STILL for Jose, so I said no. There was absolutely no attraction to Mark! But then Jose started dating this other girl, and I got so mad that I called Mark up and we started dating. It was solely to make Jose jealous, which did work, I'm sure because he started offering to give me rides home and things.
Time went on and Mark and I got to know each other. He had just gotten out of a relationship also, so we were both using each other in one form or other. The first couple years were the hardest. I was still in love with Jose and would have dumped Mark had Jose given me any reason to. But until that happened, Mark was my best friend and I didn't want to lose him. Mark proposed to me on our one year anniversary. I told him yes but that I wasnt ready to get married. When I was 20, I found out that Jose lost his virginity to a so called friend of mine, who didn't speak spanish. So you can imagine my anger.
That was it with Jose! I waited long enough and it caused undue arguements between Mark and I. I think I initiated arguements and found flaws in him, so that I didn't feel bad about longing for someone else. Time went by and I realized that even though I wasn't in love with Mark, I loved him with all my heart. We got married on our fifth year anniversary.
I won't lie, sometimes I do still feel that need for something more. I have never known the feeling of being with someone you utterly adore and are deeply in love with. I think of Mark as my soulmate, but in reality, I am still not sexually or physically attracted to him. But he is a darn good man and my best friend. I could tell him anything. He is a good provider and really caring. I know that I will never find someone better matched for me. I look beyond the things I am missing, and look at what I have. I wouldn't trade him for the world, most of the time.

Don't get me wrong, we still have our heated disputes.
I think you need to look at the big picture. Are you satisfied with what you have? Is needing more and curiousity worth more to you? I agree with your family. If you give up what you have, there may be no going back. I wish I could help more but this is something you will have to decide for yourself. Good luck.