Yuuuup
Yea at first I also thought that it was chang's grandma but it was ed's grandpa you can see his bald head, but yea this theory can also be total bullshit and Chang can be a total ass hole.....I mean he is an ass hole for all those problems he created for our mc.... only time will reveal that whether he is a sweet AH or a shitty one
The one he's loansharking is Ed's father, the person who actually showed up in the hospital is Chang's grandmother who Ed stayed with a lot of the time as a kid because his parents were often absent or abusive. She lets him stay because Ed looks like her older grandson (Chang's Hyung) who died when he was young. Due to her dementia she forgot that Chang's older brother ever died and apparently also that Chang was ever born.
Its just my assumption, that may be chang use to like Ed before ( as a brother or romantically I don't know).....as we all know he doesn't do a very respectful job for living, so may be Ed had that accident because of him....or he thought it happened because of him...in any case may be that's why he became hostile towards Ed to show everyone that he doesn't like him.......I know that it may not be true but really couldn't stop my over imaginative ass to stop exploring it's world.... he heヾ(☆▽☆)