So... is he talking about Taylor? Because eight years ago was 2012 (Jesus fucking Christ, I'm so old) and it's the year he married Taylor. And she did not lie about her age: he went to New Mexico to have sex with her a few months after "meeting" her on Twitter, her dad kicked him away, and they got hitched as soon as she turned eighteen.
He also dated Shiloh when she was 17, going as far as meeting her in PA so that having sex with her wouldn't be illegal (even if it was illegal because he had crossed state lines to meet her).
He also dated Sarah, who he met when she was 14, who lived in his house on and off from her 16th birthday onwards, and with whom he had sex with two days after her 18th birthday. Now, I'm not an expert in human psychology, but something tells me Greg was giving Sarah a lil' bit of attention before she turned 18, if he was so ready to have sex with her as soon as she became legal.