My brother's girlfriend is boring and I can't hold a conversation with her?

I'm not trying to be mean but I think his girlfriend has zero personality, I tried to get along with her but I just don't find her interesting. I think he's only dating her because she's physically attractive and has big boobs. Should I keep trying to talk to her and find something we both have in common?
My brother's girlfriend is boring and I can't hold a conversation with her?
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