The phrase "relative strangers" refers to people who may be connected or related in some way, but don't know each other very well. They are not complete strangers, but they don't have a close or familiar relationship either. Full definition
I'd attended on my own and didn't want to dance with relative strangers. (inspiringwit.com)
How do a group of relative strangers become family? (openadopt.org)
Ultimately Short Term 12 is about life's small victories and the deep empathy that people are capable of feeling for relative strangers. (trespassmag.com)