Tri-custody refers to three people, as opposed to two people, having custody of a child. This can happen in situations where a standard two-person couple does not exist, but instead a polyamorous three-person one does.
In March 2017, a New York judge awarded tri-custody to three people regarding one boy. This ruling could set a new legal precedent regarding custody in polyamorous couples. The judge in this case granted tri-custody because he believed that the ideal situation for the boy in question would be to have the two mothers have full legal custody in addition to the one father. The judge felt that this was the ideal situation for the child, as the four of them had already been functioning as a family for some time, and the boy was attached to both mothers.