Do you ever go to your sibling's workplace, if it's there to pick them up, just to talk to them, or more likely, there to buy something and has nothing to do with seeing them? How do they react?
I worked at the bookstore at my junior college as a temporary job for two weeks, and my sister came in during the first day, and I gave her an awkward smile and she responded with an irritated face. Also, my sister works at a grocery store, and once I popped in there to pick her up, and when she saw me walking through an aisle, she said "please leave."
She's kinda bitter sometimes...