Sebastian is on the left and Ciel's father is on the right. It's not hard to tell they are both from Black Butler. I got this from a video which I will share in a link below. The video is by SimplyGrouch and he goes on to explain that the author meant to do this on purpose. The author also stated that she hates drawing them side by side for this very reason. She did not elaborate however as to why she made them so alike or why she hates drawing them side by side.
https://youtu.be/UjansUvR7Sg
For those who want to check this out on the video, it is number 10 on the list