Prolog is excellent for queries on relational data (as in the Mathematical sense of a "relation"), e.g.,

born(charles, elizabeth2, philip).
born(anne,    elizabeth2, philip).
born(andrew,  elizabeth2, philip).
born(edward,  elizabeth2, philip).

born(diana,   frances,    edwardSpencer).

born(william, diana,      charles).
born(henry,   diana,      charles).

? born(S, elizabeth2, Y) and born(G, M, S).

born(charles, elizabeth2, philip). born(anne, elizabeth2, philip). born(andrew, elizabeth2, philip). born(edward, elizabeth2, philip). born(diana, frances, edwardSpencer). born(william, diana, charles). born(henry, diana, charles). ? born(S, elizabeth2, Y) and born(G, M, S).

output area

Also see [aunts and uncles].