You would think that family would always have each other’s back — but unfortunately for one newly engaged guy, his own stepmother had selfish intentions when she tried to sabotage one of the happiest days of his life.

The Gen Zer took to the R/AITA Forum on Reddit to vent — which has since been taken down — about his recent dilemma, where his dad’s wife thought her son was a better match for the OP’s fiancée.

That’s a head spinner for sure.

The original poster explained how he first met his girlfriend, Cara, when they both worked for an ambulance company. “We clicked and have been good friends since; then during the pandemic I asked her out [on a] date, and we have been together since,” he wrote.

In the early stages of their relationship, the OP brought his girlfriend around his father, stepmom and stepbrother — which seemed to go over well except for his stepsibling, Tom, being a little too interested in Cara.

“Tom during this time was becoming a little annoying coming over my apartment more frequently, and texting Cara a lot,” the 24-year-old wrote.

This is when things really got weird: “My stepmother asked if Tom could move in with us… we have an extra bedroom in the house we are renting, it was a guest bedroom,” he wrote.

From there, lines were crossed and boundaries were overstepped — as Tom began inserting himself into the couple’s life a little too much.

Then, when the OP’s stepmom found out that he was proposing to Cara, she did not handle the news well, tried to do anything to delay him popping the question — and then she did the unthinkable by sending a very risky text.

“[Karen, his stepmother] blew up my phone saying how could I do this to Tom!!!” the OP wrote about his stepmother, who told him, “Tom is in love with Cara and she is his one and only.”

“She was calling texting non stop now saying can I just let Tom have Cara,” the OP continued. He responded back saying, “Cara is a human and she isn’t something to be given away, and she doesn’t belong to anybody.”

Talk about a doozy of a situation.

Appalled commenters chimed in with their advice.

“You need to go very low to no contact with Karen, and no contact with Tom. There is something off about both of them. It’s not your responsibility to worry about what your dad does. He will make his own decisions.”

“I had a feeling as you described it that Karen was indulging Tom and encouraging him in his unhealthy fascination with an unavailable woman.”

“Get a restraining order.”

This isn’t the first time a mother of some sort has tried to sabotage a relationship.

One frustrated woman wrote to Dear Abby asking for advice on how to deal with her toxic mother-in-law, who was putting her marriage in danger.

“For 17 years, she has essentially stabbed me in the back. At my husband’s request, I forgave her each time. I love him, but I have come to realize he always takes her side. In his eyes, she can do no wrong,” she wrote.

“Six years ago, we had an issue regarding her spanking my children. I asked to meet in a neutral location to discuss it, but she and my husband’s stepfather refused. To resolve the situation, I agreed to meet at their home under one condition: If an argument began, my husband and I would leave. We even drove there separately.”

“To top it off, my husband and his mother have been putting ideas into one of our children’s heads, and now he is telling me I make everything awkward and I should fix the problem.”