They had the best room in the house with a view of the ocean. And they were out of town. I didn't expect my baby brother's nurse to walk in and have a fit.

Best advice - stay out of your kid's sex lives. If you mess things up, they'll look back on what should have been a wonderful memory with justified bitterness.

As Mr. Tennis pointed out, she may not be "legal." In most states a 2-year age difference is enough to make the situation statutory rape, and bets are off once you son turns 18 (the 2-years may not apply.) You had a glimpse of this girl, which means she could be anything from a very mature 14/13 to 25/35.

A bigger question that strikes me if your age assessment is right is that her parents were not concerned that she did not come home? In my experience most parents of 14-16 year old daughters would be frantic if she was absent over-night, and really would be frantic if it was at a mystery boy's home, whose parent they never met.

Is she using birth control ... umm, well, to be blunt, usually parents arrange for their under-17 daughters to get protection if they think they are sexually active, and well, her parents do not sound very responsible.

You know, Peyote isn't so much an anti-Semitic as he is a misogynist. (Learn to identify irrational hatreds at www.patheticmen.org.)

CT's being rational, and other posters (e.g. Exquisite Koi) are being helpful. My two cents:

1. You should be familiar with anyone getting laid in your house. I think this is a truly generalizable rule. Fits all situations and all people. Any girls he doesn't want to introduce to you and then spend time together with aren't poke-worthy anyway.

2. Yes. Yes. Yes. All the birth control talk, yes. As a sexual mentor, however, you should also point out the gravest danger of condom usage. Don't use one one time, one time only, and you'll NEVER want to use them again. Remember the future is uncertain, and you can never go home again. He's happy now getting laid while wearing a rubber. Make sure he knows that innocence is bliss.

3. Talk to her parents, and, if at all possible, arrange for everyone involved to be waiting in the living room the next time they do the deed. There are only so many chances in life to deeply humiliate and alienate your teenagers. Why not maximize the amount of shame and humiliation available here? Grandparents! Have both maternal grandmothers bring them some juice, just as they reach their noisiest. Seriously, measure just exactly how comfortable he is with sharing sexual details, and go just beyond that. Send him how-to articles about prostate massages, you know, stuff like that. IT IS YOUR SACRED RESPONSIBILITY AS A FATHER TO GIVE HIM HELL ABOUT THIS! Just exactly the right amount, though.

4. Laugh. Backstop him regarding his responsibilities while acknowledging his joy. And make sure everyone treats the young woman with respect.

Um--well I've never been a parent, but having once had parents, it always freaks me out when parents kick their parental guidance into high gear the minute that this time in their teens' life comes (inevitably, folks! get that through your head, eh?) around.

The legal question is a drag, because my first two girlfriends were underage, when I was 17 and 18, and it seems to me that the number of people who lose their virginity between 14 and 18 (and 18, I think, was the age of consent in my state) is close enough to everybody that it's absolutely ridiculous, say, to jail some poor kid of 18 or 19 for sleeping with someone 15. So I really detest the parents or grandparents who would do so. I think they should be ashamed. It's different, of course, if one person's in their 20s or more, and waaay different if someone's under 14. But I know that for some people, they'd say "under 16 is outrageous," or "under 18," and some parents go higher and higher than that. So I don't think there'll be an easy answer to that question. It's sort of as if the main question you want to ask the kid is, "does this girl have any insane parents or grandparents that will ruin your life simply in order to cockblock you both?"

But aside from that question, I sort of feel that as long as both kids are in their teens, and over 16, it's time to say "it's going to happen now, and fooling ourselves about that is idiotic." And also, I hate to say it, but I feel like saying MYOB! Some teens may feel comfortable enough discussing this sort of thing with their folks up, down and sideways, but my feeling at that age was, could anyone not planning to be in bed with me--in other words, absolutely everyone except the girl--please go away and mind your own business and pretend not to notice anything's going on?

You're having your first relationship. It's complicated enough, working out the relationship with the other person involved--I'm soooo glad that my parents and hers were cool enough that I wasn't cursed with having to multiply every long, involved relationship conversation by every parent of everyone involved as well. I would have wanted to stick my head in a plastic bag. I'd say that conversations about being careful, birth control, respect, etc. etc., should be drilled into people's heads long before the big moment arrives. Don't control-freak your kid. And don't assuage some anxiety that you won't seem like a responsible enough parent to Dr. Phil or whoever by thinking, "well if my kid's not tortured enough by this birds-and-bees talk I'm forcing him into, then I must not have made it quite endless enough!" At a certain point, you must let your kid direct this part of his or her own life.

I don't think much more advice is needed here. I'll bet on some level the father is proud of the son. On another level, jealous.

The father's role is to say "Not here! Not yet! Be careful!" But it's too bad the LW isn't a big brother. A big brother can give much better advice, with much less awkwardness. There's something very embarrassing about penis-talk with dad.

As a big brother, telling him about condoms isn't enough. Take him to the store, show him what's available. Tell him why lubricated is better. Show him the other stuff he might want to buy -- practical stuff.

Then take him to the library and find a book about STDs. Look at those fun pictures!

Might also want to sit down with an Excel spreadsheet and chart out the cost of having a baby. Or maybe watch a documentary about abortion. Scare that kid flaccid!

Seriously, though, don't assume your 17-year-old has half a clue what he's doing, even if he acts like he's got it all under control, and he's Mr. Super-Cool Babe Wrangler. He doesn't know what the hell he's doing. He just knows there's this little thing down there that is like a magnet and makes him follow bipeds with jiggly parts.

The best advice a big bro can give is about how to perform cunnilingus. Drawing a picture helps. Sam Kinison's advice isn't bad either. But I guess that isn't appropriate here.

I would think, though, that in addition to condom/STD/house-rules etc., a father ought to at least tell a son some reasonable things about making women happy. About not being selfish. About being creative and making the experience mean something more than endorphin release.