In Texas, an informal marriage requires an agreement between the man and woman, holding out to the world they are married, and living together. Of course, you have the past divorce, which could strike strongly against an informal marriage.
To make sure there is no problem, you could go get a marriage certificate. If you are just worried about the legal aspects, perhaps have the spouse sign a power of attorney or use your will to determine what happens after. Without knowing exactly what it is you are concerned about, that is the best answer to your question.
Disclaimer: This answer is intended for informational and educational purposes only and should not be considered legal advice or forming the attorney client relationship. Please consult a lawyer before taking any action.
I agree with Mr. Harding.
You would need to establish the existence of a informal or common law marriage after the other party died. That is not an easy thing to do, but is possible.
If you're concerned about inheritance from each other, you should either get married, which will allow the Texas laws of intestate succession to kick in on behalf of the surviving spouse --OR-- write a simple Will, witnessed by at least two people, and self-proved.
Since you and she have started living together again, have you filed Joint tax returns? Are you both covered under the same health insurance policy? Have you told anyone you were husband and wife? The existence of a common law marriage is a "fact question" to be established under the circumstances of each case UNLESS you both go to the county clerk's office and file a certificate of the existence of a common law marriage.
You might also consider writing wills. You don't have to be married to name someone as a beneficiary of your estate. If you die without a will, then the survivor would have to show the existence of a common law marriage by the facts and circumstances UNLESS the common law marriage is registered with the county clerk.