Well, we couldn't really afford to travel business class, except perhaps for a very very special occasion, and I admit it would be nice to do so, especially on long haul flights.
But it is not envy that makes me think it odd that KA would make this arrangement for herself and her children. I would feel most uncomfortable and uneasy if my children were sitting somewhere else, partly because if something untoward happened - such as excessive turbulence or one of them feeling ill - they would want to be near me and I would want to be near them. Also, don't you chat with your children occasionally?
Having said that, a friend of mine and her husband always used to go on holiday abroad without their children, leaving them with one or other of their parents. I used to think it was awful. We have remained friends - even though she moved to the USA many years ago - and I know her girls and their families are very loving and close so presumably these separate holidays didn't cause any resentment or damage their relationship.
I still think it's odd though.