Edessa
Joscelin II
Joscelin II is often criticized for being a lesser man than his father, but I'm hard-pressed to tell much difference, except that his father won more battles. Sometimes that's the only measure that counts.
He continued to feud with Antioch, as his father had. The feud passed to a new generation, with Joscelin at Edessa and Raymond at Antioch. They quarreled on numerous petty points, but also managed to work together when needed. They fought side by side when Emperor John Comnenus came down to Syria. In fact, when John made a move to exert direct control in Antioch, Joscelin stirred up the mob against him and helped Raymond keep his position. After 1140, Raymond was technically Joscelin's overlord.
None of that mattered. When convenient, each betrayed the other, and the two northern Crusader states failed to present a united front against the danger of Zengi, the atabeg of Mosul.
Joscelin's other concern was Cilicia, again the same as had been the case with his father. Whenever there was opportunity, he tried to meddle in that Christian state on his northern border, but conditions were different. The Byzantine emperor John was energetic and determined to re-assert Byzantine influence. More often than not, Joscelin's meddling backfired and he wound up with less, rather than more, influence in Cilicia.
Fortunately for Edessa, Zengi was repeatedly distracted by problems within the Islamic world. Some of these were of his own making, particularly his burning desire to become lord of Damascus. Indeed, for about a decade Damascus and Jerusalem were allies, for both feared the Turkish atabeg. In other cases, Zengi had the usual problems with rebellions and power struggles within his own ranks and cities. The result was a couple of long stretches (three or four years) in which he was not pressing against the Crusader states.