It's common knowledge that the British royal family is very rich. It is also well known that the Spencers, the family to which Princess Diana belonged, are wealthy as well — the personal net worth of Charles Spencer, Diana's younger brother, is estimated to be around $150 million.
As for the Princess herself, we know that she received a hefty sum of $22.5 million, plus her annual alimony payments, from Prince Charles after their divorce.
It is reasonable — and correct — to assume that, by the moment of her tragic death, Princess Diana had amassed a sizable fortune. According to her will, some of that fortune had to go to her many godchildren and her long-time butler, Paul Burrell, and the remaining sum would be divided equally between her sons, William and Harry.
So how much did each Prince get?
Princess Diana's estate was worth $35.6 million. Her sons were just 15 and 12 at the time of the fatal car accident, so as Diana's will stipulated, their money was put in a trust. She wanted each of her sons to inherit his half on his 25th birthday. However, it appears that Diana had made a serious error by naming her mother and sister the executors overseeing the will.
Complicated legal machinations on the part of the latter two have followed. As a result, the age at which the princes were going to inherit their mother's money was pushed from 25 to an unprecedented 30, and the amounts of their inheritance were reduced.
In the end, William and Harry got slightly above $16 million each. Still not a paltry sum, but their mother's family had clearly benefited at their expense.
In addition to those lump sums, Princess Diana also set up a special discretionary fund. Once the princes marry, they and their spouses were supposed to be given access to it — and it looks like this plan has worked. The discretionary fund initially amounted only to $125 thousand, and that's why this part of Diana's inheritance is often neglected. But over time, the fund grew larger due to interest and income from assets added to it.
We can assume that the princes were allowed access to the fund's money as soon as they married their spouses: William at the age of 28, and Harry at the age of 33.