title: Wikidata query does not give expected results
body: <p>I want to get humans whose parents who are not married (the parents are not in each others spouse property), so I write the following query</p>
  
  <pre><code>SELECT ?human ?father ?mother ?someone ?humanLabel ?fatherLabel ?motherLabel ?someoneLabel WHERE {
    ?human wdt:P31 wd:Q5.
    ?human wdt:P22 ?father.
    ?human wdt:P25 ?mother.
    ?father wdt:P26 ?someone.
    FILTER (?mother != ?someone)
    SERVICE wikibase:label { bd:serviceParam wikibase:language "en" }
   }limit 100
  </code></pre>
  
  <p>Then I discover if one person has several spouses, then the results give me lots of garbage. take Q15904745 as an example, his father(Q198042) has 2 spouse records, and his mother(Q16603522) is one of the spouse, but his info still will returns and i do not want to include this. </p>
  
  <p>I would like to ask how can I change my query to get what I want? Here is the <a href="https://query.wikidata.org/" rel="nofollow noreferrer">link</a> to Wikidata endpoint.</p>