WITH cl(id, idpotomok) AS (
  (SELECT c1.id, c2.id
  FROM rn_clovek c1, rn_clovek c2
  WHERE (c2.id_otec=c1.id AND c1.id_otec IS NULL)

  UNION ALL

  SELECT c1.id, c2.id
  FROM rn_clovek c1, rn_clovek c2
  WHERE (c2.id_matka=c1.id AND c1.id_matka IS NULL) 
  )
  UNION ALL
  (  
  SELECT cl.idpotomok, c.id
  FROM rn_clovek c, cl
  WHERE cl.idpotomok=c.id_otec

  UNION ALL

  SELECT cl.idpotomok, c.id
  FROM rn_clovek c, cl
  WHERE cl.idpotomok=c.id_matka
  )
  UNION ALL
  (  
  SELECT cl.id, c.id
  FROM rn_clovek c, cl
  WHERE cl.idpotomok=c.id_otec

  UNION ALL

  SELECT cl.id, c.id
  FROM rn_clovek c, cl
  WHERE cl.idpotomok=c.id_matka
  )

)
SELECT potomok.meno, potomok.priezvisko, otec.meno, otec.priezvisko
FROM cl
JOIN rn_clovek otec ON otec.id=cl.id
JOIN rn_clovek potomok ON potomok.id=cl.idpotomok

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WITH cl(id, idpotomok) AS (
  (SELECT c1.id, c2.id
  FROM rn_clovek c1, rn_clovek c2
  WHERE (c2.id_otec=c1.id AND c1.id_otec IS NULL) or (c2.id_matka=c1.id AND c1.id_matka IS NULL)
  )
  UNION ALL
  (  
  SELECT cl.idpotomok, c.id
  FROM rn_clovek c, cl
  WHERE cl.idpotomok=c.id_otec or cl.idpotomok=c.id_matka
  )
  UNION ALL
  (  
  SELECT cl.id, c.id
  FROM rn_clovek c, cl
  WHERE cl.idpotomok=c.id_otec or cl.idpotomok=c.id_matka
  )

),
temp(id,idpotomok) AS(
  SELECT DISTINCT id, idpotomok
  FROM cl
)
SELECT potomok.meno, potomok.priezvisko, otec.meno, otec.priezvisko
FROM temp 
JOIN rn_clovek otec ON otec.id=temp.id
JOIN rn_clovek potomok ON potomok.id=temp.idpotomok
WHERE otec.pohlavie='M'