It’s especially weird when it’s your sibling/parent’s friend. The worse case of this that ever happened to me was my cousin’s girlfriend ‘cause not only did I not want to talk to her it also felt very awkward.
I’m much more on the introverted side, my cousin’s more of an ambivert, and she’s extroverted.
So I’m at the park flaying frisbee with my dog, but she’s there having a picnic with her family.
She noticed me ‘cause I sorta’ stood out there in the middle of the field yelling German to an 80 lbs dog, so she ran over and introduced me to her family and it’s pretty awkward being introduced to people as “My boyfriends cousin”.