Sono is of my design. I never saw you're OC until now. I made him a long while ago on general Zoi's pony creator (around 2 years ago), even before I made my tumblr. I used the pony creator picture for my tumblr up until now. (cymphium.tumblr.com). I did not steal your OC design.
No. That's unreasonable. We both came up with our own designs independently. If I used your logic, then I would've asked you to change your design, which I have no right to do. The same applies to you.