I must say that I did not see this coming, Hades has stepped his game up but whether or not he is genuine it yet to be seen because as we know Hades needs true love kiss in order to become human again. Hades did the unexpected and proposed to Zelena after playing on her insecurities of her family issues, asking her on bending knees to make chaos with him. Zelena did not give him an answer, but it seem like she has fallen for him, which creates a problem for the heroes. After confronting Zelena about her growing feeling for Hades, Regina gathers the Heroes to discuss how to stop them from making chaos. The Heroes recruit Cora to help them convince Zelena not to give into Hades' scheme, but when facing Zelena after giving her up as a child thing did not go as plan. However, after Cora’s apology and plan failed and the sisters were about to fight Cora had no choice but to confesses to the sisters that they knew and loved each other as children after they met when Zelena healed Regina after a mishap using Cora’s wand. This confession and reunion of her daughters were enough to allow Cora to move on to a better place leaving the sister embracing each other and Regina supporting Zelena’s decision to be with Hades. Meanwhile, James took his jealousy of his twin brother to a hold new level and ambushed him in the middle of the street stabbing him and locking in the cell at the precinct and impersonated into his family. James plans to get rid of Emma and Robin with Cruella's help by using Zelena's child as leverage over Hades, but his attempt ended in tragically in spite of David attempt to save him. Finally, Gold finds a loophole in his attempt to save Belle, and with the help of Pan takes Zelena while she was in route to see Hades.
As for whether or not the sisters relationship will last, I think that they will be willing to try, but with Gold and Peter Pan taking Zelena hostage, I think the heroes will have to work with Hades to get Zelena back, which is going to be interesting to watch if the writers choose to go in that direction.