Eww, siblings are gross!

Blackmail him but let it continue. Think of it as an extra income.

Change your locks! That's super gross and disrespectful

"Look, Bro, when I said, get a room, I didn't mean MY room!"

At least now you know where the extra crust on the sheets is coming from. At least it's a close DNA match to your own.

If he is going to use your place as a hotel then you need to charge like a hotel

"Oh, that's just naaaasty!" -Cleveland Brown

Someone has to have fun in your bed . Lol but change your locks , set some boundaries. It's not okay to invite a slew of sexual partners to YOUR home. Like if he pisses them off it's your home they will turn up at.

At least it was not your wife, girlfriend or boss? Make him wash the fucking sheets!

Honestly I'd let him keep doing but require payment if he refuses I'd change the locks