How to Do It is Slate’s sex advice column. Have a question? Send it to Stoya and Rich here. It’s anonymous! Dear How to Do It, I’m an 18-year-old guy, and I’ve recently had to move in with my older sister and her husband. My brother-in-law, “Kenneth,” is honestly the most amazing guy I’ve ever met. He’s kind, funny, and built like a Greek god. He’s also super traditional and religious, which is pa...