A pregnant woman on Reddit is heartbroken after her husband declared his love for her sister.

The woman, who is six months pregnant, explained on Reddit that her sister is her best friend, as well as one of the only family members she speaks to as she is estranged from her "passive mom and abusive stepdad."

The woman explained her sister is super protective of her, and has acted as her support system throughout her life.

"When she left for college she let me stay in her bed while she slept on the floor in her student room on the days I managed to run away from home. When I turned 16, she let me move in with her permanently. We never saw our parents again," she wrote via Reddit, according to The Mirror.

She detailed that her sister and husband have always got along, and even have the "same sense of humor, love for music, books, movies and games."

"It’s like a weird perverted thing that I found the male version of my sister to fall in love with. They get along very well and that was so important to me because they’re my only family. We got married a year ago after six years together and I’m 27 weeks pregnant now with our first baby," she wrote.

However, the woman noticed her husband started acting strange when her sister began dating someone new. He never wanted to hang out with them as a group.

"[My sister's boyfriend] got along very well with me and my husband although I always felt that my husband never really liked the guy. When I asked him once why he didn’t like him, he got flustered and told me that he didn’t know it was noticeable and apologized. He told me he just didn’t think he was good enough for her," she shared.

Things reached a tipping point after the woman's sister got engaged.

"We were just having pizzas and they were having beers on my sister's balcony and the boyfriend just suddenly went down on his knees and took out a ring. She was very surprised but happy all the same and said yes," she continued.

When she and her husband returned home, though, her husband started to cry.

"I asked him what’s going on and he told me that he was in love with my sister, and has been for years but that he knew how wrong this was. I’m shocked and full of anxiety. I don’t know what to do or how to feel about this," she wrote.

Now, the woman doesn't know what to do.

"Nothing can be the same again but she’s my only family and my best friend. And my husband ... Is this over? I have been so blind ... now I see everything, of course he’s in love with her. How could I be shocked now? Can I save this marriage? And my baby? I promised her a better life than the one I had. I promised her kind and loving parents. I can’t let her come to this world with estranged parents and new people in their lives. What can I do?" she asked Reddit.

Users tried to comfort the woman in the comments, but many suggested she should leave her husband.

"You should be in shock and you’re dealing with this and everything it means head on. Talk to your therapist about it. This wasn’t an affair and he didn’t cheat. He’s been in fantasy land," one person wrote.

"You will forever be comparing yourself to her and doubting his love for you. Do not ever let someone 'settle' for you, or you will miss out on an amazing connection you could have in this life with someone else deserving of you," another commented.

Celebrity Siblings Who've Co-Starred On-Screen

More From WTBD-FM