Families that have children who are adopted, or stepchildren who haven’t been legally adopted, face unique estate planning challenges. Additional consideration must be taken when a family includes an unmarried couple in a long-term relationship and one person has biological or adopted children. If your family’s makeup is as such, it’s important to understand your estate planning options.

Treated as equals

Adopted children are placed on an equal footing with biological children in most situations for estate planning purposes. Thus, adopted and biological children are treated the same way under a state’s intestate succession laws, which controls who inherits property in the absence of a will.

In addition, adopted children generally are treated identically to biological children for purposes of wills or trusts that provide for gifts or distributions to a class of persons, such as “children,” “grandchildren” or “lineal descendants” — even if the child was adopted after the will or trust was executed.

No inheritance rights unless adopted

Stepchildren generally don’t have any inheritance rights with respect to their parents’ new spouses unless the spouse legally adopts them. If you have stepchildren and want them to share in your estate, you should either adopt them or amend your estate plan to provide for them expressly.

Of course, estate planning isn’t the only reason to adopt stepchildren. Adoption also gives you all of the legal rights of a parent during your life.

Before you adopt stepchildren, however, you and your spouse should consider the potential effect on their ability to inherit from (or through) their other biological parent’s relatives. In most states, when a child is adopted by a stepparent, the adoption decree severs the parent-child relationship with the other biological parent and his or her family. That means the child can’t inherit from that biological parent’s branch of the family — and vice versa — through intestate succession.

Second-parent adoption considerations

A growing minority of states now permit second-parent adoptions, in which an unmarried person adopts his or her partner’s biological or adopted children without terminating the partner’s parental rights. However, in states that recognize second-parent adoptions, their intestate succession laws may not provide for a child to inherit from the “second parent.”

For unmarried couples who can’t obtain a second-parent adoption, or choose not to, estate planning is especially critical — if they want the “nonparent” to have custody of the child should the “parent” die or become incapacitated and if the nonparent wants the child to inherit from him or her.

First, the parent should consider using a power of attorney for parental authority and appointing the nonparent as a guardian to ensure that he or she can act on the child’s behalf and has priority over the parent’s blood relatives in the event the parent dies or becomes incapacitated. Second, both partners should amend their wills. The parent’s will should name his or her partner as the child’s guardian, and the nonparent’s will should spell out any property to be inherited by the child.

Spell out your wishes

If you have children who are adopted or stepchildren whom you haven’t legally adopted, or you’re unmarried but in a long-term relationship and your partner has biological or adopted children, clearly address your intentions in your will or living trust. Your estate planning advisor can help you understand your options.