Not sure what the right query is for number 6

Kings The kings and queens of England are listed in a relation Kings(name nickname house,beginReign endReign). Their name is unique, either using a Roman numeral to distinguish them, e.g., 'Edward I' or 'Edward II, or in a few cases using their nickname, e.g., Edward the Confessor. The attribute nickname is an additional appelation, if they have one and it is not used in their name to distinguish them, e.g.. "The Unready'. The value of nickname is NULL if there is no nickname. The attribute house is the dynasty, e.g., Tudor Attribute beginReign and endReign are integers, the first and last years, respectively, that the king or queen was on the throne There is also a relation Parents(child. parent). Both attributes are the names of kings or queens, with the obvious connection that the first is a child of the second. Write the following queries 1. Who was king in the year 1000?e the name and nickname 2. Find all the pairs of kings or queens (A,B) such that A was the great grandchild of B 3. Find the name and nickname of all kings or queens that have a nickname that does not begin with "The" 4. Find the names of those kings or queens that were the parent of two or more kings or queens. List each such person only once 5. Find for each house the number of kings or queens of that house 6. Several times in British history, kings or queens have deposed one another, so that their reigns overlapped. Find all such pairs, listing the pairs in both orders; i.e., list both (AB) and (B.A). However, be careful not to list pairs A and B where the only overlap is that A's reign ended in the same year that B's began, or vice-versa