DP's Mum called up DP today. Their car has died (engine problem). They want to borrow our car for then next few months (DP has a work vehicle, so we can still get around). Now normally I would say yes, except, DP's Dad has had a few knocks in his own car recently. He needs his eyes tested but will not have them tested. DP's sister phoned DP today, to tell him she was in the car when FIL had a small accident (which MIL knows nothing about). I love DP's Dad, but do not want him driving our car, or any car. How the hell do I handle this? Delicately? As MIL and FIL are prone to emotional freak-outs.