I would take him aside and tell him if he loved this girl, if she is in his heart, to do the honorable thing and step up and take her for his own. The emotional bond that takes place when we give it with love is here for a reason too. I believe we are meant to have only one mate forever. I know, I've had far more than my share. None, though they were exciting and had us zooming around the moon, were like the first. The first was clean and pure and sweet, the stuff of which life is made.
On the one hand, I think you have something. My first, we were both virgins and it was a special sort of intimacy. There was a bond in the figuring it all out together, exploring each other. And if you keep it to that, there's a sort of innocence. We broke up because of our long-distance relationship, but if we ended up married, I sort of doubt that bond alone could have kept the relationship going. Hell, it didn't overcome the distance gap and there's a lot more involved in marriage. There's a lot more involved in a relationship than the fact that you were each other's first. I think the evidence shows so many kids marrying their high-school sweethearts (and presumably their first sexual partners), and end up divorced in a few years. Sex is often mistaken for love. And for virgins, this is even moreso.
For a good relationship, the people have to be compatible and going in the same directions. How many people are the same person they were, with the same views and goals as they were when they got out of high school? I'm certainly not. I've probably been about the same from age 25. But I did a lot of growing up and finding myself from age 18 to 25. Part of that was dating several people and learning to find and pursue the compatible girls, not just the ones that I could have sex with. If I had gotten married to the girl I lost it to, I'd probably be miserable today. So, I'd recommend waiting until he's at least out of college and to date several girls in the meantime. Living with one or two may not be a bad idea either. It's a great lesson for learning to adapt to the opposite sex in everyday life, from sharing a sink to just learning how to deal with somebody else at home all the time. And waiting usually puts you in a better financial position to pay bills and enjoy your marriage. Not spend the first few critical years, struggling to survive.
The whole JW thing was, in my experience, an extremely poor way of getting to know anyone enough to find a compatible mate. Your experiences may vary from mine. Being obligated to find a JW girl, where's the first place you look? Your Hall. Ok, there's about 6-10 single girls my age (actually pretty high compared to other Halls with 1 or 2 girls) and most were OK looking (though my superficial younger self had higher goals). Of course, those girls also had to have an interest in you. If it didn't work with those girls, there's always circuit and district assemblies. Now you find a girl, talk to her for a little bit to see if there's any interest, then try to schedule more time with her. Generally, that time was under the watchful eye of a chaperone, where nobody is going to be themselves. It's bad enough on one-on-one dates that each one is so busy trying to be on best behavior, they don't act themselves. With chaperones, it's nearly impossible. Where I was, once you even started this dating process, it was considered serious. I've had fathers on the first date ask what my intentions were. It was as if that first step, asking somebody out, was a road to marriage. Whereas the worldly kids would date casually. You'd spend some time with several girls to get to know them better. But that was not proper. Dating was serious and a road to marriage, not to try a bunch to see who you like best. And of course, no sex as a JW. What guy isn't a bundle of raging hormones? The only way to "get some" is to get married. So, it seemed, you'd marry the first girl you sort of got along with and had this sort of "puppy love" affection for based on seeing each other on your best behavior. Neither really knows the other until they get married and out on their own. Then they discover that one is a slob and drives the other nuts. Or that the guy leaves the toilet seat up. Or they squeeze the tube from the bottom.
In my opinion, you should have several partners, live with a few, wait until you're older, and find somebody who's also a good friend. And live with him/her before getting married too.