The Collaborative International Dictionary of English v.0.48:

Congenerous \Con*gen"er*ous\, a. [L. congener; con- + genus,
   generis, birth, kind, race. See Genus, and cf. Congener.]
   Allied in origin or cause; congeneric; as, congenerous
   diseases. [Obs.] --Sir T. Browne. -- Con*gen"er*ous*ness,
   n. [Obs.] --Hallywell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

congenerous
    adj 1: belonging to the same genus [syn: congeneric,
           congenerical, congenerous]