Well, that's annoying. You are not alone. So much so, here is a whole article on it. https://www.medicalnewstoday.com/articles/326897 Are you over weight at all? That can be a contributing factor. Losing some weight may help. Secondly, hormones may contribute. When is the last time you had those checked? This is a newer problem? I ask because sweat glands can also be the issue but this has not always been a problem for you so their placement isn't likely the cause. Although, they could have issues.
Stress can make us sweat more. There are also underlying conditions that can lead to it such as hyperthyroidism. Also something called hyper hydrosis. Hyper hydrosis often happens due to an underlying condition as well such as diabetes, low blood sugar, nervous system disorders. So, this is important to talk to your doctor about to figure out if there is any other health condition leading to his excessive but sweating.
You should wear breathable, moisture wicking material for your underwear. Cotton over polyester. ;) But the type they use in athletic garments is best. I got some for my son at a hiking store/website. Wipe yourself down. Change often. What about trying an antiperspirant there? Probably wouldn't hurt. Might work well. They make starch powder these days (do not use talc) and you could try that.
But really, the big thing is that the sweat is not dangerous, mostly a nuisance. However, is it because of an underlying condition you need to treat? That's what you must figure out!