Re: So true...
It most certainly is not true of the Rothschilds
You've picked what are very much the poster family for passing on wealth and influence. For many families it only takes one or two children to overdose, crash their learjet, or turn their latest Ferrari into wreckage to bring about an end of their family line.
Concentrating wealth becomes progressively harder the more children you divide it between. Once the four john-boys die, they'll have left their estate to > 4 people, effectively diluting themselves.
Moving wealth down below the grand children is exceptionally hard - see the Hilton family. Their last best hope is ......