The Massachusetts law is still evolving but in child custody disputes there are significant advantages to a parent that adopts a child and the Massachusetts courts is still having issues addressing where a child is the biological offspring of one parent but the other parent did not complete the formal adoption process prior to the divorce.
If there is the opportunity to do a legal adoption that would be the safest issue. In addition, having both parents’ names appear on the child’s birth certificate as the biological or the adoptive parents can help, but it is not a perfect scenario.
There are some issues in terms of if one of the parents is not the biological or legal parent under the adoption may in circumstances be treated similar to a step-parent. Massachusetts does allow some rights regarding what is called “De Facto Parents” in a child’s life; including being granted visitation rights even if the biological or legal parent objects.
It is evolving and there can be complicated issues. It would make sense to both talk to an attorney before the child’s birth or after the child’s birth and certainly if you are going through a divorce.