Does my Boyfriend have a crush on my sister?

I have known my boyfriend for 4 years now, but we just start dating recently. He had always being my friend, he (my currently boyfriend) used to talk about girls with me. He even told me, he had crush on 4 girls at same time. he later told me he had a crush on me but was afraid to get rejected and those feeling are back. I didn't return his feelings, since i had a boyfriend. I know he easily falls for a girl, cause every girl he knows, he use to have a crush on them. 2 year later, me and my ex broke up and half year later we start dating. He had never seeing my sister before beside pictures from her Facebook. my sister is much prettier than me. first time he met her, he kept staring at her and i couldn't even gets his attention. He was looking at her and laughing with her. Second time we met her, I felt it so annoying, he won't even look at me, never saw him looking at someone, like he was looking at her. I was needed to call his name many times before he reacts to it. I told him , that i feel weird that he keeps staring at my sister for hours. and he told me he didn't knew he was staring at her for so long, So 2 week ago, we went to see her again, since my mom was there to cook some food for us On his way to her apartment, he was so excited, not sure if its for the food or my sister. again I notice that he was staring at my sister for 4 hours. recently i notice that he bring my sister up, and he even made plans to go fishing with her and her boyfriend without telling me that they was planing to go fishing. We was invited by my dad to celebrate his birthday and my boyfriend got annoying and said to me , why is your sister not coming? didn't she say yes to come to your dads birthday? Sorry for my English, i don´t use English that much. can someone help me and explain it to me. Am i overreacting? thinking to much , all in my head or there is something weird going on? forgot to mention my boyfriend and my sister have a lot in common.
Does my Boyfriend have a crush on my sister?
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