No, you can't. There's nothing illegal about having a 15 year old girlfriend, provided you aren't having sex. And, call me old fashioned, but you shouldn't be having sex until you know each other really well anyway...
As for a romantic relationship at 15, well... lots of people had relationships with older partners in their mid-teens and claim to be the better for it. Lots of people were abused and manipulated by older partners, and are scarred for life. Our experiences color our perceptions, so whether it's "OK" will depend greatly on who you ask. In reality, it depends on three major factors:
- Your level of commitment.
- Her maturity level.
- Her parents' approval.
Your level of commitment.
It's bad enough to promise an experienced adult the world, and then dump her when you get bored. Doing it to a young adult is utterly unconscionable. If you're not willing to do whatever it takes to make the relationship work, don't waste your time or her heart.
Her maturity level.
Make an HONEST evaluation of her maturity. I know 16 year olds who are more mature than a lot of 40 year old "successful" adults. I also know 16 year olds who really should just go back and start over with 2nd grade. Maturity is the primary determining factor in an age-gap relationship. If she's physically 15 and mentally 19 or 20, I don't see anything wrong it. If she's 15 and acting like it, the relationship will likely get tiring and oppressive rather quickly, as you are repeatedly subject to her childish whims and fantasies.
Her parents' approval.
If you're going to do it, her parents need to be in the loop. If you can't approach them about it, you shouldn't be in the relationship - when they find out themselves, you'll be lucky if it's just her father chasing you with a shotgun. Her parents are going to want to know what your intentions are, where you are with their daughter at all times, what you're doing, etc. They need to trust you to take care of her.
Another big thing to consider is that a 15/16 year old's world is very different from a 20 year old's world. You're most likely in the middle of college, starting a career, and thinking about your future. A 16 year old is in high school, flipping burgers for McDonald's at best, and thinking about whether or not that cute boy in homeroom has a crush on her. If she's a mature 16 year old, this won't be as much the case, but it's still a completely different world for her. A relationship would necessitate reconciling these differences, and finding some sort of common ground on which to build said relationship. She's not going to live with you until she turns 18 or so (otherwise
nobody will believe you're not sleeping with her), so it's going to STAY different worlds for quite some time.
It's important not to over-fantasize the relationship. Think about it realistically, critically analyze potential problem areas, and then decide if it's really worth the time and effort.
All that being said, both you and I have probably garnered a reputation as closet pedophiles (
), but I stand by what I said. There are a lot more factors at work than blindly setting "moral" limits at arbitrary age boundaries. Hell, in other cultures people are marrying and having children in their mid teens. Not that I think that's a particularly good idea, but nobody there seems to be complaining. Then again, in other cultures women aren't allowed to complain, so... Anyway, the relationship you're describing can be beneficial or destructive, depending mainly on how YOU handle it. Either way, it certainly won't be as simple as dating someone your own age. If you can't accept that, don't even consider such a relationship. If you truly love her, I say go for it, if you can make it work, and her parents approve. If you REALLY love her, and her parents say "no," you can always wait a few years until she's older. Nobody said love came easy...
Note: I don't really think this extends as far down as relationships much younger than 15, with a handful of VERY rare exceptions. But 15, almost 16, is pretty damn close to adulthood for some people. (Considerably less so for others.)