Why doesn’t he avoid being around me?

This happened over a month ago - me & my brothers friend who Iv known for many years kissed when we was both drinking at a party, told each other we fancied each other but he has a girlfriend currently so we decided to keep it between us both that it happened. My brother stayed at mine over the weekend & then rang his mate to come over for dinner ( he was at his GFs when my bro rang him ) he said cool and showed up with a gift, which I was pretty surprised about because I thought perhaps he’d want to avoid being around me? Makes me think he has no respect for his girlfriend? I did feel super anxious at first then I was like ah whatever and we was all just having a laugh like we usually do. I did also catch him a few times just staring at me which was slightly odd.
Why doesn’t he avoid being around me?
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