My Sister is My Mother: A Complicated Family Drama

My Sister is My Mother: A Complicated Family Drama

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I heard a story somewhere and I remembered that I have watched a Korean drama with such a plot, however I don’t recall which one it was. I don’t even know if it’s a plot or sub-plot. I hope you guys can help me. Here’s the story: A man finds out that his mom has gave birth to him in very young age, so the mom’s parents registered the boy as their own. So his older sister which he adored is actually his mother and the parents are his grandparents.