Niklaus was usually always one step ahead of everything, of everyone, but this time he's been careless. He gave these annoying children the occasion to steal from him, to take his most important belongings : the coffins––all five of them––which undoubtedly lead to this.
Of course Elijah wouldn't pass the occasion to be the noble brother, and Klaus has had the oh wonderful surprise to see all of his siblings back to life. It was now the first time in about nine centuries that the Mikaelson family was whole again.
Klaus wasn't delusional, he knew it was only the beginning of trouble. One coffin was still left to be opened, one still missing, the one that was the dearest to him : Kaylah's coffin. He had to get it back before any of his siblings could see it, before Kol could see her.
FLASH_BACK (960 A.D) :
At first Kaylah had been too shocked to react at all, it had felt so unreal. She viewed him as a friend, one of her closest friends who also happened to be her husband's brother. Niklaus and Elijah's relationship with Tatia gave her the occasion to spend a great amount of time with him. She hadn't seen that coming, he was in love with her sister, why would he try to kiss her? She was so angry at him, her sense of betrayal burning brighter than a bonfire.
"Kaya, please!" Niklaus nearly pleaded, desperation clear in his blue eyes, as he reached for her wrist before she could move past him.
"I don't want to hear another word, Niklaus! You do not get call me that, anymore; only my friends do, and you're not my friend. When Kol will learn about this, you'll be over!"
She seethes through gritted teeth, freeing herself from his hold before turning her back on him and angrily walk away. She couldn't believe his guts, after the way they treated her older sister––and seeing how it dramatically ended for her––he dares to come to her and try to take advantage of her in her time of despair? She had lost everything, turned into a bloodsucking demon! And well, she was his brother's wife for the Gods' sake! Did that meant nothing at all to him?
Klaus' eyes widen and he couldn't formulate his thoughts any longer. Kol couldn't hear about this. He would never forgive him. He was the most temperamental of the family, worse than him, he'd never go past it. Never. Kaylah was his, he always considered as his, even before she became his wife- ...Oh Gods, she's his wife now! Klaus gulped down. He couldn't allow it. No. Not after the Tatia debacle. He couldn't let her mutter a word about it.
...He had to keep her quiet.
Whatever the consequences.
END OF FLASH_BACK.