I cannot tell if this is Nanase Haruka, a bigger version of Ciel phantomhive or his father.
And in the tag was written “Nezumi”.
It’s Nezumi. He has short hair in the original novels. This is a novel art. It was taken from a No.6 photo-album on pixiv tagged solely as No.6 and Nezumi’s name. You can click on the art and check the album if you’d like ^___^