"Am I married?" Seems like a simple question, right? But, sometimes it isn't, and the answer to that question can be surprising.
Common Law Marriage
"Common Law" marriage exists in Texas, although legally it is called "Informal Marriage". The basic test is that the man and woman: (a) agree to be married; (b) live together as husband and wife in Texas; and (c) 'hold out' to others that they are married. TxFamCode 2.401. The main issue that most people face is the 'holding out' question, which is to say that they told or implied to third parties (in Texas) that they were married. This can be established all kinds of ways, such as by tax returns, testimony of others, etc. A case I had in the past revolved around what was being claimed on health insurance.
Texas also has "Putative Marriages", which are basically an otherwise valid marriage that is invalid because of a legal obstacle of one or both parties. A common example would be that the husband's divorce from his first wife is not final when he marries Wife #2. Once the obstacle is removed, then the marriage becomes valid. These situations are quite rare in our times.
Note : There is no such thing in Texas a "Palimony" or similar. In other words, you cannot gain rights under the Texas Family Code because you lived with someone over a long period of time, absent a marriage of some type.