The last time I was in Target, I think it was Hanes (for females) underwear had a variety of waist and leg cuts and one of them was especially made for low cut jeans. I don’t know that they would offer enough support for a fellow’s jewels though. Not sure if you use some type of tucking or supporting device.
Here is a page with some reviews on those underwear at Walmart. There are mixed reviews, but a lot of people seemed to like them. In general, I like Hanes brand undies.