====== Relationships ======
{{tag>family}}
===== Description =====
Defining family relationships.


**Source**:  The Art of Prolog

===== Download =====
Program source code: {{relationships.pl}}


===== Listing =====
<code prolog>
uncle(Uncle,Person) :-

	brother(Uncle,Parent), parent(Parent,Person).



sibling(Sib1,Sib2) :-

	parent(Parent,Sib1), parent(Parent,SIb2), Sib1 \= Sib2.



cousin(Cousin1,Cousin2) :-

	parent(Parent1,Cousin1),

	parent(Parent2,Cousin2),

	sibling(Parent1,Parent2).



%Program 2.1:  Defining family relationships



</code>
===== Comments =====
Luck of definition of brother in family2