The question of whether a mother or father is more likely to get full, sole custody of their child is an interesting one. In the late 1800’s, a legal principle in family common law, known as the Tender Years doctrine, was commonly called upon to argue that the mother should have custody of the child. The idea behind the doctrine is that in the “tender years” of the child, a colloquial term referring to childhood and adolescence, it would be cruel to create any space between a mother and her young child, and that a child in these tender years needs all of the love and affection that only a mother can give. Granted, it was not written into the law, and it served more as an assumed presumption, one that was adopted by some courts in the U.S. from a custody law that was passed by British Parliament in the mid-1800’s. Still, it persisted in child custody battles for over one hundred years.
However, as time went on, the courts stopped recognizing the presumption, and actually went back and started reversing decisions that were heavily based on the tender years presumption, and the courts began ruling based on rather gender-neutral respects. That is why in most of the country, the court determine custody with the best interests of the child as the primary factor, where the presumption is that the primary caretaker is going to be the best parent to handle the primary responsibilities and custody of their small child.
However, there is a bit of similarity in these two determinants. In many instances, granting the mother sole custody is in the best interests of the child, either because the father is not a fit parent in his own right, or because the father moved significantly far, to the point that it would do more harm than good to relocate the child. But, keep in mind that, if the roles were reversed, these same reasons could be behind the rationale behind why a court would grant the father sole custody.