As Leticia says by the time I retired everyone was younger including all the bosses.. I never had a problem with it and as far as I'm aware neither did they... It never bothered me that my immediate boss and most of the other bosses were younger some of them as has been said were younger than my children. I can't remember it being an area of conflict for anybody in fact I was often asked for advice by my very young colleagues.
The only thing I did find was how aware some of them were of my limitations, my job was sometimes very heavy physically and several of my colleagues whom I'd know for a long time and had become friends would take the heavier workload from me, which in my last couple of years working I was very grateful for. There were never any conflicts that I remember.