NOTE OF CAUTION: Russian Tortoises are like potato chips, you can have one, if you're very strict with yourself, but you'll find that eventually you search for ways to aquire more and more of them!!! lol (i'm working on aquiring a 5th)
If you're looking for a "friend" for your tort go female all the way!!! Two females will be MUCH happier than a pair, especially since one pair won't typically mate due to increased stress on the female...These guys (and gals) do better in herds of 2 females to 1 male ratios....
EDIT: torts can be sexually mature in and around 10 yrs of age...which, if wild caught can be difficult to determine