Have not read other replies but as they speak another language my first gut feel is either
Your hubby has sibblings. No doubt if there realky is some issue at play it had been discussed at some level. Can he approach one of his sibblings and ask for some info?
Religious .... are you the same religous belief to them? Do you still practice? Not many raise kids with any depth of religous upbringing these days. Could your kids have repeated something or said sone thing that up set them?
Cultural .... you could ask similar questions to above.
The older generation oz muh more aet in their ways and less likely to yield.
When imigrants come to Australia it is not unusal for them to get caught in a 'time warp' and while things have changed bak in their home land they live day to day life like the day they left.
There are so many variables it is hard to say without ibserving the situation as close as an outsider can.