Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
relative [ˈrɛlətɪv] n (member of family) ро́дственник[-ица]
adj (comparative) относи́тельный*относи́телен (connected)
relative to относя́щийся к +dat
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.