After an event, my sister told my boyfriend it was nice seeing him?

One time when my family and my boyfriend gathered for a meal, my sister asked for my boyfriend's phone number before leaving, saying that she would text/call him about job questions. They're not in the same or similar field, but I guess a company can hire people of different fields, so I didn't think much of it.

The other night, my mom, sister and I carpooled with my boyfriend to an event of a relative's since it was a far drive and didn't make sense to drive more than one cars since we live within 15 minutes from one another.

When my boyfriend dropped my sister off (my boyfriend was staying over at my place, so I was still in the car - apparently), I heard my sister said to my boyfriend it was nice/good seeing him just as she was getting off the car.

We said to our cousins it was nice seeing them when we were at the event. I think that's something we would say to our cousins. Yeah I see my sister, but not very often, maybe once every few months. I didn't get a "nice seeing you" but my boyfriend did. I'm not sure what that meant? 🤔

I've noticed that in my sister and my texts in the past, my sister has said to tell my boyfriend something, or hope that my boyfriend was / was not, certain way, before she got his phone number. For example, she hoped that he was feeling okay. I'm just making an example. I don't remember the specifics since I kind of just let that go, but now I do recall there were times when my sister seemed to put emphasis on my boyfriend, and when I didn't reply to her text (s) about my boyfriend, I saw her text mentioning the same again.

I have the tendency to overthink, but I try not to. Am I just overthinking this? I don't doubt my boyfriend and don't think he would be interested in my sister, but I'm not sure if my sister *is* interested in my boyfriend?
After an event, my sister told my boyfriend it was nice seeing him?
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