On 21 August 1881, Salome (Gonzalez) Gonzalez my 2nd great grandmother gave birth to her 9th and 10th children. It is amazing the size of families our ancestors created, but to imagine having natural twins that far down the birth order in 1881 is incredible. Luckily, in a time of high mother and infant mortality, she survived that birth and lived to be at least 83 years old.
When their father Nestor went to record the births in the Civil Register of Births for Santander Jimenez, Tamaulipas, they are named Doniciana and Doniciano. 
I had been combing the birth records of this town building this family tree. Every time I added an addition name, I would then search for other marriage and death records trying to build out their lives.
But the twins disappeared. It was difficult enough to come up with either a Doniciana or Doniciano Gonzalez in records, let alone, finding good candidates based on birth year. Sadly I assumed they had died young, so I combed the death records for the date directly following their births. Nothing! I was relieved but frustrated. I moved on.
Months later, I realized I had missed a whole set of baptism records. Not that I was looking for one person in particular for I would spend hours in front of the computer reading records, page by page. One night, while reviewing these missed records, I came across another set of twins for Salome and her husband Nestor. They were named Maximiana and Maximiano. How cute; but another set of twins for this poor woman!!
As I went about recording their baptisms, I was struck by the year. The baptism record indicated the birthdate of the twins; it was the same birthdate as Doniciana and Doniciano.
No wonder I could not find anything else out about them. Had they change their names or did the person recording their births get it wrong?
Not that I am absolutely sure I found them in adulthood. But that is another story.