I'm curious if they'll be splitting the monarchy between the children or keeping it consistent. Government could actually change quite a bit at this point across much of the west.
Technically there is no one who could authorize that split except the current monarch. I'd imagine things will continue just as they were
That said, there is precedent. Victoria didn't inherit Hanover, which had been in personal union with the UK, because it had different succession laws (which excluded women). So it's just a matter of political will really.