My bf has something that looks like that. I’ve never asked him what it is though.

I second the sacral dimple. I have one and my son has a slight one.

2 of my boys have a sacral dimple. Theirs don’t cause a gluteal cleft like this, but I’ve done so much research on sacral dimples, that it is very common for it to look like this. Sometimes it doesn’t lead to anything. My husband also has one, and he had a cyst develop inside of it. I wouldn’t worry about it for now, but mention it at his next appointment just to keep an eye on it.

My nephew had an extra vertebre it look like a tail sticking out. They have to wait until he is older to try to remove it because his spinal cord is wrapped around it.

Looks like a sacral dimple