Am I doing something wrong by being in love with my aunt's ex husband? Should I tell her about it?

He's not that old, he have a son he's 6 years old and he loves me too. I was baby sitting his son since he was younger because he's mother's kind of selfish. I don't have to explain my whole life but i felt something for him and he felt it too we start getting close to each other more than before and we actually had sex many times. I don't know if i should tell her anything about our relationship and i don't know if we're making something wrong but i was sure that he won't back to her.
Am I doing something wrong by being in love with my aunt's ex husband? Should I tell her about it?
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