I don't think you need to give the conclusion of killing the brother in the logline.? I also don't see any reason to mention she has 2 cloned children.? ?I would simply say something like this:

"Impeded by her own brother, a genetically enhanced woman finds she has the power to kill with just her thoughts and unleashes this power to save her children."

A biologically enhanced mother plans for more clone children, but she must make the world a place where they can survive, so she unleashes her ability to kill using only her brain, kills her brother.