The Collaborative International Dictionary of English v.0.48:

Filiation \Fil`i*a"tion\, n. [LL. filiatio, fr. L. filius son:
   cf. F. filiation. See Filial.]
   1. The relationship of a son or child to a parent, esp. to a
      father.
      [1913 Webster]

            The relation of paternity and filiation. --Sir M.
                                                  Hale.
      [1913 Webster]

   2. (Law) The assignment of a bastard child to some one as its
      father; affiliation. --Smart.
      [1913 Webster]

   3. Descent from, or as if from, a parent; relationship like
      that of a son; as, to determine the filiation of a
      language.
      [Webster 1913 Suppl.]

   4. One that is derived from a parent or source; an offshoot;
      as, the filiations are from a common stock.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

filiation
    n 1: the kinship relation between an individual and the
         individual's progenitors [syn: descent, line of
         descent, lineage, filiation]
    2: inherited properties shared with others of your bloodline
       [syn: ancestry, lineage, derivation, filiation]

Moby Thesaurus II by Grady Ward, 1.0:

158 Moby Thesaurus words for "filiation":
   Indian file, accord, addition, adjunct, affairs, affiliation,
   affinity, agnation, alliance, ancestry, apparentation,
   approximation, array, articulation, assemblage, association, bank,
   birth, blood, blood relationship, bloodline, bond, branch, breed,
   brotherhood, brothership, buzz, catena, catenation, chain,
   chain reaction, chaining, closeness, cognation, combination,
   common ancestry, common descent, concatenation, connectedness,
   connection, consanguinity, consecution, contiguity, continuum,
   contrariety, course, cousinhood, cousinship, cycle, dealings,
   deduction, derivation, descent, direct line, disjunction,
   distaff side, drone, enation, endless belt, endless round,
   extraction, family, fatherhood, female line, file, fraternity,
   gamut, gradation, homology, house, hum, intercourse, intimacy,
   junction, kindred, kinship, liaison, line, line of descent,
   lineage, link, linkage, linking, male line, maternity,
   matrilineage, matriliny, matrisib, matrocliny, monotone,
   motherhood, mutual attraction, nearness, nexus, offset, offshoot,
   paternity, patrilineage, patriliny, patrisib, patrocliny, pendulum,
   periodicity, phylum, plenum, powder train, progression,
   propinquity, proximity, queue, race, range, rank, rapport,
   recurrence, relatedness, relation, relations, relationship,
   reticulation, rotation, round, routine, row, run, scale, seed,
   sept, sequence, series, shoot, sibship, side, similarity,
   single file, sisterhood, sistership, spear side, spectrum,
   spindle side, sprout, stem, stirps, stock, strain, string,
   succession, swath, sword side, sympathy, thread, tie, tie-in, tier,
   ties of blood, train, union, windrow



Bouvier's Law Dictionary, Revised 6th Ed (1856):

FILIATION, civil law. The descent of son or daughter, with regard to his or
her father, mother, and their ancestors.
     2. Nature always points out the mother by evident signs, and whether
married or not, she is always certain: mater semper certa est, etiamsi vulgo
conceperit. There is not the same certainty with regard to the father, and
the relation may not know or feign ignorance as to the paternity the law has
therefore established a legal presumption to serve as a foundation for
paternity and filiation.
     3. When the mother is or has been married, her husband is presumed to
be the father of the children born during the coverture, or within a
competent time afterwards; whether they were conceived during the coverture
or not: pater is est quem nuptice demonstrant.
     4. This rule is founded on two presumptions; one on the cohabitation
before the birth of the child; and the other that the mother has faithfully
observed the vow she made to her husband.
     5. This presumption may, however, be rebutted by showing either that
there has been no cohabitation, or some physical or other impossibility that
the husband could be the father. See Access; Bastard; Gestation; Natural
children; Paternity; Putative father. 1 Bouv. Inst. n. 302, et seq.