Why these people say this about me on the bus?

I'm quiet person at school and this two girl & boy was talking about me and looking at me saying "Im glad she's not my sister" and the girl said "ewww" while I'm just minding my own business. I stay to myself not bothering nobody. But people still find ways to talk shit about me and isolate me.
Why these people say this about me on the bus?
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