Had the EXACT same problem with my 1986 2.3-16V last week. The problem started in the *feel* of the clutch pedal while being depressed -- soft for the first 20%, then very little resistance the rest of the way down (still driveable, but worrysome). This developed into full scale clutch-pedal-to-the floor with no resistance except the return spring. I also had to slip my foot under the pedal to bring it back up. Needless to say, I could not disengage the clutch plates, therefore could not get it into gear (thus, could not move the car from out of my garage). Had to have it towed to my shop
Bottom line: New clutch Master AND Slave cylinders -- it drives like new now!
Have your brother check the clutch master cylinder first. It's the one attached to the clutch pedal. See if it's leaking any fluid down the side -- I'm willing to bet it does. Note: He might have to remove the knee bolster panel to see it.
Good luck and let us know the outcome.