A friend of a friend is most often not an enemy, no. But it is not impossible. If everyone were allies to their allies allies (heh), things would quickly get out of hands.
Person A:"Haven't you heard? The Crimson Wings allied with the Intrepid Adventurers, who are allied to the Ukulele Warriors. Which means that we are allied, since they are allied to our common allies the Merchants of R'tall!"
Person B:"No, the Ukulele warriors are enemies to the Rewarding Flames, who are allies to the Crimson Wings, so technically, we're enemies."
Person A:"Or allies."
Person B: "Yeah. Exactly."
Al extrañar un amigo bueno siempre me siento algo melancólica...