Author Stella Harris has a lot to share on the topic of threesomes as it is the subject of her most recent book "The Ultimate Guide To Threesomes" (Simon & Schuster). As a certified intimacy educator and sex coach, she gives her students the tools and confidence to explore their sexuality safely and free of shame. Book is available here: https://www.amazon.com/Ultimate-Guide-Threesomes-Stella-Harris/dp/1627783075