The medieval Irish legal tradition placed a high value on the presence and social function of the child within the community, understanding the practice of child-rearing to be undertaken for the well-being (socamail) of the household. For social stability, a child ought to be the product of a union sanctioned by both affected kin-groups and preferably from parents within a common social bracket. And in all likelihood, this was the norm. A person's legal worth and status at birth could determine not only the manner of upbringing, but also ultimately a person's legal standing and the nature and extent of any involvement within the community. In a society like early Ireland, however, where a variety of sexual relationships were either permitted, acknowledged or refuted, legal concern centred on what impact various unions and separations might bring to bear on the kin-groups involved. Sexual relationships (whether by choice or circumstance) involving people of different social status, and with the possibility of procreation as an outcome, certainly piqued the interest of the medieval legal scholar. Ill-made contracts could be altered, rebalanced or rescinded; was a child a different matter? The modest aim of this contribution, therefore, is to venture into what Thomas Charles-Edwards has described as the ‘penumbra’ that surrounded established kinship in order to probe core legal impediments to kin-affiliation, while seeking to consider what path the medieval Irish legal commentators might advocate to resolve the fundamental issue of establishing a person's place within a kin and the community in turn.