Bobby Singer is an old time hunter based in South Dakota. A
life long bachelor, he runs a salvage yard and an auto shop
out of his home, along with his rotweiller Rumsfeld.
He's an old acquaintance of John Winchester, and has
threatened to shoot him on more than a dozen occasions. But
through his friendship with the elder Winchester, he watched
the boys, Dean and Sam, grow up from wet behind the ears
kids to hunters with their own fearsome reputation.
He's a researcher, and has (or knows how to get) any source
of information that a hunter might find useful. His house is a
cyclone of papers and books and maps, all organized to his
own system that no one else can quite figure out.
When Dean and Sam (or John's Boys, as he often refers to
them) get themselves into a mess they can't get out of on their
own), Bobby's the one they call and is usually the
one to find the solution. He's got a deep affection
for those boys, an honorary uncle of sorts. And he
doesn't let them try to pull any crap over on him.
When the boys get pulled into a government
conspiracy involving a eugenics lab and demons in
high government positions, they call on Bobby.
When it comes to organizing the other children like
Sam rescued from the eugenics lab, Bobby is there.
Heck when it came to the rescue of Sam from the
government, Bobby was forefront on the planning
stages.
Whether he realizes it or not, Bobby Singer is the
rock that the Winchesters depend on.