WHAT IS THE DATE OF HIS CHILD
SELECT ?value1 ?value2 WHERE { wd:Q105013 p:P40 ?s . ?s ps:P40 wd:Q50993 . ?s pq:P569 ?value1 . ?s pq:P570 ?value2 }
frederick william i of prussia: Q105013 prince henry of prussia: Q50993