"In 1976, a man won a contest to name the Seattle Mariners and then disappeared without a trace"

Kiro7 has a long write-up of their effort to unravel the mystery including using Ancestry.com, knocking on doors and:

We mapped out a full family tree, finding a nephew, a niece, her children, an uncle, a cousin, and a second cousin.

...

We reached out to all of them, with email, phone calls, text messages, and social media messages, including Facebook and LinkedIn.

They got a response:

Roger’s niece said they were all still big Mariners fans, but are private people, requesting that we end our correspondence with them.