Prior to the Obergefell decision many same-sex couples did estate planning to try to get similar rights to heterosexual married couples in the event your partner passed away. One of the estate planning tools that was used actually tapped into the family law world which was to do an adult adoption. This adult adoption established a parent-child relationship between the couple. And this estate planning tool is what can prevent you from now getting married.
While that made sense a few years ago, this estate planning tool will actually create issues for that couple if they now want to get married because you cannot marry your child or your parent. So legally, if you get married it would be a void marriage as a result of the adoption. This could create significant challenges in both probate and divorce situations if or when they arise.
In the context of probate, anyone challenging the inheritance rights of the spouse might prevail because the marriage itself is void. This would leave your spouse out of some of the inheritance rights of your spouse and instead default to the inheritance rights of your spouse, but not as your spouse, rather as your child.
In the context of divorce, you may find that since the marriage was not legal it is thus void and therefore, the Court cannot divide the community property estate because there is no community property.
If this is your situation, prior to getting married, you should consult with an attorney to determine the best manner to ensure that your marriage will be valid. If you have already married but did not do anything with regard to the adoption you need to contact an attorney to resolve this issue.