I have not been able to successfully kill the two brothers, without killing the two [censored]s as well, in the Golden Cat mission, while maintaining a GHOST undetected . I have used stop time but somehow the girls detect me, even if I knock them out too before stop time has completed. I know I have played the rest of the level undetected because when I kill them both with rats and finish the level the same way, I receive the GHOST undetected.

Anyone able to kill only the brothers and still receive undetected?

Do you have Time Bend II? They can still see you with only Time Bend I.

Yes I was using bend time II

I asked my friend to do this and he said he shot at the brother and strangled the girl before the end time ended. So evidently you have to take care of both of them before the stop time ends, or they will be alerted to you, even if they are in the middle of a choke hold. Not sure if the game designers meant for this to happen but that is definitely how it works.