What are adoptive parents rights if a child is a part of another will?

I am not entirely sure I understand the situation, because I'm not sure what you mean when you say that the birth mother left the adopted child a trust which was set up by the aunt. I am going to assume that you mean the child's birth mother's Will provided for a trust to be created by the child, with a relative of the birth mother (perhaps her sister) nominated as the Trustee of the trust. (A Trustee does not set up a trust, they manage a trust which was created by a trust grantor or testator, if the trust is created by a Will). The child would not have been considered a legal heir of the birth mother after the adoption was completed, and the "aunt," assuming she is a relative of the birth mother and not the adoptive parents, is not legally related to the child. However, the birth mother was free to leave assets in trust for the child even though they were not legally related, and she was also free to select a trustee who she knew and trusted, without regard to the preferences of the child's parents. So the only real question here is whether the Trustee of that trust can be changed now to someone the child's parents would prefer. The adoption really hasn't got anything to do with it. Neither does the biological relationship. If the trust provides for a way that the Trustee can be changed, then that will normally control. If it doesn't, then you have to look to the law of the state which controls the trust (if the trust was established by a Georgia resident's Will and set up to use Georgia law, that may be Georgia) to see whether and how a trustee can be changed. The child's parents may be able to take action on behalf of the child, if the child is under 18 years old, but the actions they can take are going to be limited to the actions permitted by the trust or by applicable law. Without reviewing the trust and knowing what law applies, I can't tell you whether there's any ability for the trustee to be changed easily. I can tell you that, in our firm's Wills, trustee changes are usually limited to cases where the trustee is misbehaving. It's the birth mother's Will; her wishes as to who should serve as the trustee and who she wanted to benefit are the important ones, not the wishes of the trust beneficiary or the beneficiary's parents. But the parents should seek the review and advice of a good trust attorney if they want a more specific answer as to what can be done in this case.