A good friend of mine who is a little older than I am has his grandson and wife, plus a great grandson living at his farmhouse, along with great grandmother too, and all get along famously I'm very glad to say.
However the little boy, who is about two years old, probably knows his mother is about to have another baby, so is perhaps acting up a bit because of it, and great grandad says his solution might be a small tap on the bottom.
He won't do it, quite wisely I think, and leaves it to the parents to sort these minor crises out, (great grandad being no fool, nor a soft touch generally, but of course spoiling grandchildren or great grandchildren is par for the course!