You'd be surprised at the amount of kids who think they should get an "early inheritance" or extra help towards X, because they didn't get a high paying job, or they think they deserve more money than siblings because of spurious reasons, try and get their infirm parents to change wills to their favour
When large sums of money are potentially up for grabs, a real greedy and nasty side can come out of even the nicest people.
I know people who's parents have died, and within hours of the death, random cousins etc have turned up at the house to get stuff from the house.
Another one, a long estranged son/brother, who "absolutely couldn't visit" / "lived too far away " /etc miraculously appears and suddenly decided his mother who he hadn't spoken to or seen in 7+ years was definitely not in her right mind because of what illness he thought she had, and tried to contest the will because he thought her mentally incapable.
A colleague had people turn up at her house demanding to see her mother's will, because they said her mother had "agreed" to give them some money. She didn't know who the person was, they claimed to be a long time friend of her mother's