The Collaborative International Dictionary of English v.0.48:

Parental \Pa*ren"tal\, a. [L. parentalis.]
   1. Of or pertaining to a parent or to parents; as, parental
      authority; parental obligations; parental affection.
      [1913 Webster]

   2. Becoming to, or characteristic of, parents; tender;
      affectionate; devoted; as, parental care.
      [1913 Webster]

            The careful course and parental provision of nature.
                                                  --Sir T.
                                                  Browne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

parental
    adj 1: designating the generation of organisms from which hybrid
           offspring are produced [ant: filial]
    2: relating to or characteristic of or befitting a parent;
       "parental guidance" [syn: parental, maternal, paternal]
       [ant: filial]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "parental":
   adoring, affectionate, ancestorial, ancestral, conjugal, covering,
   custodial, defensive, demonstrative, devoted, faithful, fatherlike,
   fatherly, filial, fond, fostering, grandfatherly, grandmotherly,
   grandparental, guardian, guarding, husbandly, immunizing,
   languishing, lovelorn, lovesick, lovesome, loving, maternal,
   melting, mother, motherlike, motherly, parent, paternal,
   patriarchal, preventive, prophylactic, protecting, protective,
   romantic, safeguarding, screening, sentimental, sheltering,
   shielding, soft, tender, tutelary, uxorious, vigilant, watchful,
   wifely