COUSIN, the offspring of a sibling of one’s father or mother. There is no simple common noun for this relationship in Heb. Numerous circumlocutions are found in the OT to communicate the concept. We have such phrases as “son of your father’s brother,” “father’s brother’s daughter,” and on many occasions simply “kinsman.” Although the rights and special status of cousins as such are not stipulated, it is clear from the marriage of the daughters of Zelophehad (Num 36:11), and the right of land purchase belonging to Jeremiah (Jer 32:7-12), that there were certain privileges involved. Cousins often married cousins, as it was not forbidden in the Leviticus code. In the NT the Gr. term, συγγενίς, G5151, applied to Elizabeth (Luke 1:36) can mean any sort of female relative, “kinswoman,” or person of indefinite relationship to the speaker. The word appeared in the Hel. age. It is a peculiar fem. form of the more common classical term συγγενής, G5150, “related,” “akin to” (Luke 2:44, et al.). The grammarians of the Hel. age in their attempt to preserve the syntax and morphology of the classical Attic idiom, rejected syggenis as an improper and uncouth form. The RSV tr. of “kinswoman” is thus to be preferred.
International Standard Bible Encyclopedia (1915)
Only in Col 4:10, where Mark is said to be "cousin" (Revised Version) to Barnabas, and not as in the King James Version, "sister’s son." The renderings "cousin" of the King James Version for suggenes, in Lu 1:36,58 were probably understood at the time of the translation, in the wider, and not in the more restricted, sense of the term, now almost universally prevalent. In view of this the renderings "kinswoman," "kinsfolk" in the Revised Version (British and American) are preferable. As a title of honor and dignity, it occurs in 1 Esdras 4:42, etc.