Perhaps as they are emigrating, they are treating this visit as a last ‘hurrah’, and think, ‘Well, Mum and Dad won’t be entertaining us much in the future, so may as well make the most of it whilst we can’.
Not saying that excuses their behaviour, but…
I agree, certainly don’t fall out over things though. Just not worth it when they will soon be a long way away.
He never gives up being stupid.



