Identify yourself safely and specifically
Give your name from that time, the street or area, approximate years, and one non-sensitive shared memory. Ask whether you have reached the right person before sharing private family history.
Use nostalgia as an invitation, not a claim
Say what made you think of them and invite their version of the memory. Do not post old photographs, addresses, or stories publicly without permission.
Build the present-day connection slowly
Exchange brief updates before proposing a visit or reunion. If they do not remember, do not reply, or prefer privacy, accept that without contacting relatives for access.