"descended from a common ancestor," c. 1600, from French consanguin (14c.), from Latin consanguineus "of the same blood," from assimilated form of com "with, together" (see con-) + sanguineus "of blood" (see sanguinary).
word-forming element meaning "together, with," sometimes merely intensive; it is the form of com- used in Latin before consonants except -b-, -p-, -l-, -m-, or -r-. In native English formations (such as costar), co- tends to be used where Latin would use con-.
1620s, "characterized by slaughter, attended by much bloodshed;" also bloodthirsty, eager to shed blood, delighting in carnage," from French sanguinaire or directly from Latin sanguinarius "of or pertaining to blood," also, rarely, "blood-thirsty," from sanguis (genitive sanguinis) "blood," a word of unknown origin. Latin distinguished sanguis, the generic word, from cruor "blood from a wound" (related to English raw, from PIE root *kreue-). The classical sense of "pertaining to blood" is rare in English.
<a href="https://www.etymonline.com/word/consanguine">Etymology of consanguine by etymonline</a>
Harper, D. (n.d.). Etymology of consanguine. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/consanguine