Do AIs break Alliances?

Do AIs break an Alliance with the human player?  I know that if an Alliance partner gets into a war with another AI, that the human sacrifices the Alliance if the human does not declare war on that same enemy.  But, other than that, can the human depend on an Alliance being kept?

I ask because in my current Suicidal game, the galaxy (ignoring minor races and distantly weak AIs) is now a square with a different power dominating almost exclusively a separate quadrant.  Thus, I face one AI on each of two lonnng flanks and the remaining one diagonally with little contact except right at the vertex.

If I could get an Alliance on one flank, could I war on the other without having to watch for backstabbing by my Ally?

Sadly, the two on my flanks are at war with each other, so I cannot Ally with both and attack through the vertex.  However, I might be able to get an alliance with one and then be drawn instantly into war with the other.

Or, and here is the bigger risk, I may have to declare war on one to get the Alliance with the other.  I am relucatant to do that if I can not trust the Alliance.  This is especially risky in this game, because the two AIs use different weapons.