How exactly do they work?
I know that each player has their own double ranking, but then do they average them in order to rank the double teams?

Q. How does the ATP Doubles Rankings work?

A. The ATP Doubles Ranking is based on calculating, for each player, his total points from his best 18 results from all eligible tournaments, including the Barclays ATP World Tour Finals (Doubles) played in the 52-week ranking period. For entry purposes there are no mandatory events, however, once a player is accepted in the main draw of one of these 12 tournaments, as a direct acceptance,a qualifier or a lucky loser or having accepted a wild card, his result in this tournament shall count for his ranking, whether or not he participates.

straight from the atp website

But when seeding in a tournament