Creepy couples

Posting anon just in case. I need to get this off my chest and can't find anything online about this but I know it must be common. It's happened to me twice now and I just need to vent.

Has anyone else ever had a couple befriend them, only to later reveal that they're looking for a third, a unicorn, or something else? It's bad enough when it's just one person with unclear intentions, but two makes for an unbalanced dynamic and even more difficult.

I recently befriended someone from work. He wanted me to go have dinner with him and his wife. This was one of the first times I had been out since covid, so I was nervous but excited to do something social. It was fun and we all had a good time.

About a week later, he asked me to go exercise with him, where he revealed that his wife was bi and they were interested. I said I understood, but I wasn't, no disrespect. We've hung out a couple of times since then, and it usually goes well, but they keep making subtle and outright references to being with me. At times, messages were too frequent (several times a day every day from both of them). He was edging towards being emotionally manipulative, such as guilt tripping me for not being able to hang out during finals week.

I finally put an end to it through text because I just didn't feel safe doing so in person. I was very respectful and placed no blame on them. Even though I do believe they did something wrong, I wanted to minimize any drama and didn't see the point of litigating every aspect of why it went wrong.

She didn't write back, but he did and it was pretty nasty.

Thankfully, I won't see him much at work, but I am nervous about the next time I see him. I feel like I did something wrong, but I was honest from the start and they weren't. I don't want to think the worst about people, but since this has happened twice now, I'm afraid of being extra suspicious/anti-social in the future.

Why am I writing this? Just trying to make sense of this whole thing. Any insights would be appreciated, thanks for letting me air this out.