SPARQL query on dbpedia: Find women who have husbands younger than them - sparql

Question

I am working on a fun query. In dbpedia, I want to find records of females who have married younger males. Or,alternatively, husbands who had wives older than them.
I came up this this SPARQL query. Sadly it returns too few records, only n = 3.
# I always add these for easier commandline querying
prefix dbo: <http://dbpedia.org/ontology/>
prefix dbp: <http://dbpedia.org/property/>
prefix dbr: <http://dbpedia.org/resource/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
prefix exo: <http://example.org/ontology/>
prefix xsd: <http://www.w3.org/2001/XMLSchema#>
SELECT ?husband ?husbandBirthDate ?wife ?wifeBirthDate
WHERE {
# there are 300000 triples that use dbp:spouse
# unfortunately very few have spouses which are also in dbpedia
# and for those partners the birthDate occurs even more rarely in dbpedia
{
?husband dbp:spouse ?wife .
?husband dbp:gender ?husbandGender.
FILTER(str(?husbandGender) = "male")
?husband dbp:birthDate ?husbandBirthDate .
?wife dbp:birthDate ?wifeBirthDate .
?wife dbp:gender ?wifeGender.
FILTER(str(?wifeGender) = "female") .
FILTER (?husbandBirthDate > ?wifeBirthDate)
}
UNION
# there are ~1400 triples that use dbo:husband which means "hasHusband"
{
?wife dbp:husband ?husband .
?husband dbo:birthDate ?husbandBirthDate .
?wife dbo:birthDate ?wifeBirthDate .
FILTER (?husbandBirthDate > ?wifeBirthDate)
}
UNION
# there are ~1300 triples that use dbo:wife which means "hasWife"
{
?husband dbp:wife ?wife .
?husband dbo:birthDate ?husbandBirthDate .
?wife dbo:birthDate ?wifeBirthDate .
FILTER (?husbandBirthDate > ?wifeBirthDate)
}
}
ORDER BY ?husbandBirthDate
Sadly it returns too few records,these three, (currently, 2020):
husband
husbandBirthDate
wife
wifeBirthDate
http://dbpedia.org/resource/Karel_Kosík
1926-06-26
http://dbpedia.org/resource/Růžena_Grebeníčková
1925-11-01
http://dbpedia.org/resource/Keiran_Lee
1984-01-15
http://dbpedia.org/resource/Puma_Swede
1976-09-13
http://dbpedia.org/resource/Keiran_Lee
1984-01-15
http://dbpedia.org/resource/Kirsten_Price_(actress)
1981-11-13
What am I doing wrong?
Should I switch to the foaf ontology? Do I have to explicitly parse the date with ^^xsd::date?
Note: I have my own docker-image of DBpedia, in the production version of DBpedia about 25 records are found. Still too few , I think.