You use getpos to do this eg:
Man1 SetPos [getpos Man2 select 0, getpos Man2 select 1, getpos Man2 select 2]
There may be dashes before the select I can't remember. Anyway you can add and subtact values from each coordinate eg
getpos Man2 select 0 + 2
(Puts Man1 2 metres East of Man2)
getpos Man2 select 2 + 2
(Puts Man2 2 metres above Man1)
This can also be put in a script and put in a loop so you can stay at a relative position even if the object changes location. You can therefore strap yourself to a plane or car or do many other cool things like that.
I'm not positive about the syntax but that is the general idea behind it.