Divorce is never easy. Not for either party in the disintegrating relationship — and certainly not for any children involved.

And it never makes for easy jurisprudence.

While societal norms have evolved and the traditional roles of men and women in child-rearing have changed over the years, divorce law has been slower to respond.

Now advocacy groups are pushing legislation that would require family court judges to consider joint custody of children in most divorces, unless one parent is deemed unfit. The Boston-based National Parents Organization is supporting such a bill in the Massachusetts Legislature.

The bill has the backing of more than 40 state legislators, including: Reps. Ted Speliotis, D-Danvers; Ann-Margaret Ferrante, D-Gloucester; Diana DiZoglio, D-Methuen; and Brad Hill, R-Ipswich.

The change would rectify an imbalance in the courts that favors mothers over fathers, Daniel Sabbatelli, a member of the National Parents Organization, told Statehouse reporter Christian M. Wade. Sabbatelli’s own divorce grants him limited access to his three daughters.

“The courts don’t treat both parents equal,” he said. “It’s winner-take-all.”

Critics of the bill include divorce lawyers and domestic violence advocates, who argue that custody laws must be flexible and always put the interests of children first.

“Every case is different,” Fern Frolin, a divorce attorney with the firm Mirick, O’Connell, DeMallie and Lougee, told Wade. “And this isn’t a battlefield between moms and dads, it’s about what’s in the best interests of the children.”

Indeed, the interests of the children must be the primary concern of a family court judge. Such legislation always raises difficult and troubling questions. Children will always suffer in a divorce. The goal of jurists should be to minimize that suffering.

Access to both a loving mother and a loving father is in the best interest of children. In cases in which there is no suggestion of violence or abuse by either parent, in which they are both clearly equally loving parents, more equitable custody arrangements ought to be considered. Legislators must carefully examine bills coming before them that alter custody arrangements to be certain they keep the children’s interests foremost.

Wade reports that the 2010 U.S. Census shows that women comprise 80 percent of custodial parents. It seems difficult to imagine that only 20 percent of divorced fathers are worthy of a more expansive role in the raising of the children.

Ned Holstein, founder of National Parents Organization, told Wade that courts traditionally require little of fathers other than alimony and weekend visits.

“The system encourages bitter custody battles,” Holstein said. “Whoever wins the battle gets sole custody of the kids, a boatload of child support and alimony payments. And that’s the worst possible thing for the kids.”

Massachusetts is one of 17 states weighing legislation on shared parenting arrangements. Others included Maine, Vermont and New York. The proposals range from mandating that child custody is split evenly to rewriting guidelines for judges to consider when granting joint physical custody.

Martin Healy, chief operating officer and legal counsel for the Massachusetts Bar Association, told Wade Massachusetts’ law is unique because it focuses solely on the child’s well-being. Because of that, Healy said the bar wants to uphold the state’s existing laws.

“Both parents are deemed to be fit at the outset, but there isn’t a presumption of that going into the courtroom. You have to prove it,” he said. “What it really comes down to is what is in the best interests of the child.”

On this issue, perhaps more than any other, legislators need to be thoughtful and deliberate. This is not a bill to pass or reject in the late hours at the end of the session.

The law must allow judges to do what we expect them to do: exercise good judgment. If the proposed change to custody law can preserve judicial discretion, protect children’s interests and simultaneously grant fathers greater access to their children, the Legislature should support it.