I'd never heard of this before, but it turns out my mum died at the same age as her mother - quite an early age: 67. A friend told me it's not unusual. I mentioned it at my evening class, and of seven of us, two others said that, on reflection, their father and grandfather had died at the same age. Other classmates were extremely dismissive of this being a thing.
I'm not looking for an argy-bargy, and I hope no-one will take offence, but I'd be intrigued to know if anyone else has heard of this. Also, if you think about it, has it happened with any of your ancestors?