Board Thread:Theories and Speculation/@comment-1872728-20200725151448/@comment-32685487-20200730143055

Now that I think about it, he did go to Orochimaru to try and control himself. Maybe that Curse Mark is Oro's way of trying to help him control it, or maybe it is natural for him. We don't know.

Edit

No Jugo's Cursed Seal is natural. Oro didn't make his Cursed Seals until after he learned Senjutsu, which was after Jugo had been studied by him.