He gave her a blank look for a moment even as he mimicked her movements by petting the critter in his own arms. "Well obviously I wasn't paying that much attention. Plus... I'm sure that not ALL Harkness' in existence are related to that ... man."
He gave a bored sigh. "Oh, yes, Father probably did something completely horrid and awful that haunts the... Jack still." He decided against using his fathers favorite word for the thing that shouldn't exist. He gave her a flat look. "I know the kind of man my Father is. He hardly tried to hide it from me." He'd seen people tortured and killed and made to work for the Master in using any number of ways.
"Well," Omni drawled. "That would make you my sister." No attempting to seduce her. He blinked and looked at her again. She felt... a lot like him, even that small strange hickup he could feel in his own timelord aura. One that neither the Doctor nor the Master had. She... no way... he had been told she was dead. Wouldn't be the first lie he had been told. That would mean... he jerked back with a strange ill look on his face. The anomaly was HIS father too. Then he said the revelation. "You are my sister!" Not a half sister... no... a full same parents twin sister. He looked dumbfounded.