Well, Sherlock did feel good that there was no chance that John could impregnate him. But he still wasn't sure about the other way around.

"So... " He approached the question carefully. "Because I am not a full demon, a Fallen, or an Old One, I cannot impregnate you, right? " John had been so forceful last night- he was still walking a bit tenderly and he was sure that his hole was still still open from last's nights stretching. He wondered if John would even want to be the.. receiver. He was certainly dominant when he wanted to be, which of course Sherlock quite liked.

And yet, he had to wonder.. what kind of child would it be.. one quarter demon and half vampire? Were there even quarter demons or half vampires? He had no idea.