And yet, they invited a bunch a queens.
Most of the European royals are cousins of the groom. Doesn’t explain the Middle-Eastern and Japanese royals though. Since this is only a “semi-state” wedding (a newly invented category) not a full state wedding (like Charles & Diana) heads of state and/or government aren’t being invited. The exceptions seem to be foreign royalty (family connections) and Prime Ministers and Governors-General of the Commonwealth Realms (since William is their future monarch). I think the corps diplomatique has been invited to church service itself.