What is {number of children} of {William the Silent} that is {applies to part} is {children who lived to adulthood} ?
Count the number of William who made it to the adulthood as the Silent's children life.
How many of William the Silent`s children live to adulthood?
SELECT ?o WHERE { ?t property:applies_to_part resource:children_who_lived_to_adulthood . resource:William_the_Silent property:number_of_children ?t . ?t property:number_of_children ?o }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q78454> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1971> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P518> <http://wikidata.dbpedia.org/resource/Q20483979>
} 

SELECT ?obj WHERE { wd:Q78454 p:P1971 ?s . ?s ps:P1971 ?obj . ?s pq:P518 wd:Q20483979 }