Not so much for her little brother because his personality was pretty clear from the first moment I thought of him and distinctively unusual, same with his physical appearance.
But I do have some trouble writing his best friend Jinho, and since they are always together, it basically makes them two parts of the same character XD. I know what his personality is like, but executing that feels harder than it needs to be, and I'm legit having a hard time convincing myself to leave the way I wrote him alone, but I'm just going to roll with it, and hope I get better at writing him as I go lol.