Heteronymous is defined as words that are different but that have a common relationship.(noun)
An example of words that are heteronymous are the words "brother" and "sister" which are different but have a common relationship in that the brother is the sibling of the sister and vice versa.
See heteronymous in Webster's New World College Dictionary
Origin: Gr heterōnymos < hetero, hetero- + onyma, name
See heteronymous in American Heritage Dictionary 4
Origin: From Late Greek heterōnumos
Origin: , from Greek, with a different denominator
Origin: : Greek hetero-, hetero-
Origin: + Greek onoma, name; see nō̆-men- in Indo-European roots.