Brehon law recognized ten forms of marriage/partnership, and there was no such thing as an "illigitimate child", despite rulings that dis-favored prostitution. Brehon law favored monogamous relations during the duration of each relationship.

The most favored form of marriage was the marriage between equals -- this would be a marriage of two individuals of equal status or rank. Both thus could bring into the marriage material benefit on an equivalent level. In such a relationship, the woman was considered co-lord with the man, and all contracts signed by one must be known about and agreed to with the other. Fostering of children, raising cattle, providing food for community feasts -- all this was done and agreed-to as a true partnership. After all, both were bringing in an equivalent amount of resources to facilitate each decision.