Let's say that I have a bloodline of male population Williams and Skywalker families as my knowledge base:
father(phil,tom, williams).
father(tom, bob, williams).
father(bob, robert, williams).
father(robert, steve, williams).
father(anakin, luke, skywalker)
father(luke, finn, skywalker)
father(finn, andrew, skywalker)
father( andrew, charles, skywalker)
Which rule can I use to know the oldest and youngest in bloodline?
For example
?- oldestYoungest(skywalker,X,Y)
should return
X = anakin
Y = charles