Alex was not killing the guys for a reason.
Clare wanted to check whether any of them were from her family.
She knew that it was not possible, and she knew that there was no way her family members would give in, but she still wanted to make sure.
Now Alex could just check if they were or not, and then tell her the result.
Clare won't say anything.
She knew that Alex wouldn't lie to her.
But Alex decided to wait for Clare.
That girl wanted to see it with her own eyes, so he would let her do it.
He could get the skill that the Grenefled family was hunted for by killing any one of them, so he didn't need to kill more people for it.
He would let Clare kill them.
After all, her family members were sacrificed for these assassins to have their abilities.
"At least cutting your jaws off made you guys learn how to talk without them…."
Creation is hard, cheer me up!