Responses
I think Hyewon's father used to love the Aunt but opted for hyewon's mother instead. That's why Aunt is angry with Hyewon's Mother and Father, so she plotted to kill Hyewon's parents while she was in her 10 day comma. Aunt also kills Dohwa's parent because they are trying to find the cure and that means Hyewon will be cured and she can't replace Hyewon with Yoosun (which she controls)
everyones speculating that they're sisters, but my first though was that donwha's mother was the woman who hyewon's father ran off with and was killed by hyewon's mother.
But then again still doesnt sound right ╮(￣▽￣)╭