2v2 games differ plenty than 1v1 games. Your conventional games make 2v2's like two separate 1v1's going on at once, but in RoN that's not always the case.
1. There will be a weaker and a stronger player. If your best player can take out their stronger player, then you can try to hold out vs. the weaker player and win that way. If neither of you can match their stronger player, then you'll have to plan a coordinated attack that will take out their weaker or stonger player first.
2. Team/Nation combo's that double one player can utterly defeat that player in less than 5 minutes if done correctly, and if the opposing teammate does not help in time.
3. You don't want any General Yule's. Meaning you don't want a teammate to not attack or not put any pressure on their opponent. If one of your opponent's is basically out, but the other player is booming an age or two ahead of both of you, you need one player to keep attacking, raiding, etc. to put pressure on them while your other teammate can outboom and eventually win you the game.
4. You have to plan ahead to successfully defend against getting doubled. Most of the time, this involves sending a ville to your ally in preparation to build a BX or Stables for defensive aid... or just be sure to tribute your ally some resources when they're in need. Those are the 2 ways to stop a double Ancient Age rush.