When we last saw Jaime Lannister, he was cradling the corpse of another dead Lannister — that of his daughter Myrcella. Season five of Game of Thrones featured his ill-fated trip to Dorne to rescue her, after his sister/lover Cersei received a pointed threat against the princess: a viper with a Lannister lion necklace in its mouth. "They're only two like it in the world," she said. "The one I'm wearing, and the one I gave Myrcella." (And the one Joffrey gave Sansa, and the one Tyrion gave Ros, but who's counting?)
Cersei, interpreting the threat to be from House Martell, grew livid. ("I will burn their cities to the ground if they touch her!") And so Jaime embarked on his "sensitive diplomatic mission" to extract Myrcella from Prince Doran's custody, the idea being that a stealth mission would help prevent a war, all the while not knowing the threat actually came from Ellaria Sand. It was she who ended up planting the poisoned good-bye kiss on Myrcella as she was departing Dorne to sail to King's Landing.
Just as the poison kicks in, Jaime and Myrcella finally have “the talk” — the one where he comes clean about all the twincest. "The fact that he finally told one of the kids the truth, and the daughter actually says, 'I know, and I'm happy,' and he gets so happy, and then it's all snatched away?" actor Nikolaj Coster-Waldau said at the Game of Thrones premiere. "Did they even get 10 seconds of happiness together? Not even."
Another assassinated Lannister could mean war. And so, as the ship pulls into the harbor of King's Landing at the start of season six, Jaime is faced with the prospect of having to break the news to Cersei. "It's not a great starting point to any conversation," Coster-Waldau laughed. "It's very difficult, just the idea of having to bring a mother the corpse of her dead child, especially when she expects a vibrant young lady to return."
If Jaime's mission to Dorne was in part motivated by him trying to be a good father (or even just a father, for once), his actions from here on out will be to protect what's left of his dwindling family. "Now, for Jaime,” Coster-Waldau said, “it's about trying to help Cersei.”