The other highly significant legal aspect associated with kinship relations is of sexual unions and reproduction. Inheritance seems to have been passed on primarily in the paternal line, as such, clarifying the relations between partners, who probably quite frequently were members of different kin-groups, as well as their children, must have been quite essential. The surprisingly close parallels between the early medieval Irish and Welsh laws where sexual unions are concerned, and the similarity between the most prestigious union described in them with the Gaulish marriage as described by Caesar, indicate that the treatment of different sexual unions was quite similar over wide areas of western Europe from late prehistory well into the medieval period.