POAs do not give grandparents the rights to sue for custody. Please talk to an attorney in your county. Look on this website for an attorney in your area.
Speak to a family law attorney about the particular facts of your case. Grandparents have standing to fight for custody of a grandchild under certain circumstances. A power of attorney alone does not protect parent rights. A power of attorney is giving another person the right to act on your behalf. A guadianship would be something that gives another person rights over your child and/or your assets.
A power of attorney probably has no bearing on grandparents' rights (which are very restricted in Texas). I would urge you to consult with a good family law attorney in your area. I am very familiar with the courts in Dallas County and can assure you that they will carefully follow the law on this matter, so you'll want to make sure you have a good case ready to go before you appear there.
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