In one year when I was a JW, about 8 years ago, we had 9 weddings at the Kingdom Hall, between March and September. The couples who married range from 18 to 27 in age. I remarked to an Elder we hadn't had so many weddings in a year for a long while. He said "Yeah its nice, its just a pity none of them where virgins when they walked down the aisle."
Recently having met up with some other ex-JW's, it seems its not uncommon. As one of them remarked she didn't think that anyone in her congregation between the ages of 16 to 25 hadn't had sex. She'd had sex with at least three JW brothers, one who was a Min Servant, Elders son.
My wife and I started having sex when we got engaged, which was 10 months before the wedding, and that was nearly 30 years ago now. Our attitude was that we were getting married anyway, so why not. She was 20, I was 22. In fact I don't think either of us coerced the other into it.
We got married round same time as another two couples, who we were friendly with. We used to meet for dinner parties occasionally. It used to make me laugh, because on such occasions the WT says we should talk about "spiritual things", we talked about sex. I can say one thing that the WT's attitude to oral sex and sexual positions certainly did not affect any of us. Like hell were we going to let them dictate to us what we did in our own bedroom.
Though I've been out of the JW's now for 5 years, I know from contacts, particularly those who know my children. I get told its all still going on among the young ones in the congregation.
But of course they give the impression that all is fine and that no such thing happens in the congregations of Jehovahs organisation.