Prime minister David Cameron made the announcement at a CHOGM meeting in Perth.
Another old fashioned and discriminatory rule that will be abolished is the one that says heirs who marry Catholics cannot inherit the throne.
“We will end the male primogeniture rule so that in future the order of succession should be determined simply by the order of birth,” Cameron said.
“We have agreed to scrap the rule which says that no one that marries a Roman Catholic can become monarch,” Cameron he added at a press conference.
All 16 Commonwealth countries that still have the Queen as their head of state have agreed to the changes.
The rules mean that if Prince William and Kate’s first born child is a daughter she would automatically be in line to be queen, regardless of whether she has a younger brother.
At the moment Prince Charles is next in line followed by Prince William and the Queen will probably live to be 101 like her mother so don’t hold your breath waiting for it to happen.