When using the Traders and Builders and two players have one city each with their builder in it, and that two cities become one I always asumed that the builders keep working the same way (giving a extra turn for their player).
But in one of my recent games it almost happened something that left me wondering: if one of the players sharing that city with two builders has more pawns than the other in it, does that affect the other player's builder or they would keep working like normal?
At any time when the builder is on the table, it functions as documented in the rules.
The number of builders in a single city does not affect the way in which each builder functions. Nor does the number of knights. Only the active player gets an extra play if he/she extends the road or city. A builder can be deployed even if there are thieves, knights, or builders of other players on the road or city, as long as you have a thief or knight present.
Furthermore, the builder is not counted when calculating the majority. This is because the builder is not considered a follower.
Only if, due to expansions like The Tower or The Dragon, a player's last follower is removed from a road or city, the builder will no longer function. At this point, you're supposed to return it to your supply.
