How do i stop my son from crying with family

amy • 2 kids,1 angel baby,#3 on the way married 11 years

my son started to cry with his auntie at 4 months I thought it was just her it's not just her he cry's with everyone even his dad he'll look for me when ppl hold him I don't get why he crys with ppl I have read baby's start the stranger danger stage at 9 months he started early on he's 5 1/2 months now. How do I brake him of that???