When Simon Templar, aka 'The Saint' tangled with the Longman family in the episode "The Man Who Gambled With Life', one of the Longman daughters bragged that they had quite an extensive file collected about him through their computer network. She claimed that they knew that Templar had no family. Simon took the news in stride; after all, why get upset when it was so obvious that their computer didn't have the correct information.
For Simon Templar has a son, at least in Toobworld. His name was Simon Templar as well. Simon Junior used his Daddy's nickname of "The Saint", as well as his vanity plate for his car. (He was played by Ian Ogilvy in the late 1970s in "Return Of The Saint". Daddy was of course Roger Moore in the sixties series.)
There are two other Simon Templars in the TV Universe, one played by Andrew Clarke and the other by Simon Dutton, and both in 1989. But the two of them would have to be relegated to alternate TV dimensions.