In some Eastern countries (and at least one Western state) there's a simple solution: You make an exact correspondence between how much wealth you have and how many wives you take. Thus, you have so many children that none of them can become especially wealthy.
In most of the Western world, there was a similar fix: Primogeniture. The first boy would get all the money, and the younger ones would have nothing.
Come to think about it, wouldn't that law (the richer you are, the more children you are required to have) fix a lot of problems? Inequality, dumbing down of society...
But what you miss is that socies are now far less stable than they were. In the longer long no one is longer able to have hundren, to say nothing about few thousands, like this czar from China.
In most of the Western world, there was a similar fix: Primogeniture. The first boy would get all the money, and the younger ones would have nothing.