Thank you everyone for your varied and thought provoking responses. I think janeainsworth summed things up best for me and when GS parents are around I will just have to learn to bite my tongue. I have realised that it is they who are the problem.
I will cope with this by being fair but firm when our GS is here on his own. My OH pointed out that he does eat what he is given when he cooks for him and his Parents are not around
Retiring and living frugally in money from downsizing after years of stress


