Desperation

"Master said that you are his sister. Come with us and meet your father!" Kaeldur approached Sabrina somewhat calmly as he looked at the woman who didn't seem even remotely related to Nial.

They were totally different, whether it was their demeanor, their powers, or their attitude. But that was to be expected since Sabrina and Nial were not related by blood. 

Kaeldur knew that Sabrina had yet to get to know this little piece of information. She was oblivious to the truth, though that didn't matter to Kaeldur, whose mind was filled with other things. He was more worried about Nial than Sabrina, especially because Nial was the only reason for Kaeldur to bother about Sabrina's existence in the first place.