According to Bernal Diaz del Castillo

Before speaking of the great Montezuma, and of the famous city of Mexico and the Mexicans, I should like to give an account of Doña Marina, who had been a great lady and a Cacique [lord, or leader] over towns and vassals since her childhood.  Her father and mother were lords and Caciques of a town called Paynala, which had other towns subject to it, and lay about twenty-four miles from the town of Coatzacoalcos. Her father died while she was still very young, and her mother married another Cacique, a young man, to whom she bore a son. The mother and father seem to have been very fond of this son, for they agreed that he should succeed to the Caciqueship when they were dead. To avoid any impediment, they gave Doña Marina to some Indians from Xicalango, and this they did by night in order to be unobserved. They then spread the report that the child had died; and as the daughter of one of their Indian slaves happened to die at this time, they gave it out that this was their daughter the heiress.

The Indians of Xicalango gave the child to the people of Tabasco, and the Tabascans gave her to Cortes. I myself knew her mother and her half-brother, who was then a man and ruled the town jointly with his mother, since the old lady's second husband had died. After they became Christians, the mother was called Marta and the son Lazaro. All this I know very well, because in the year 1523, after the conquest of Mexico and the other provinces and at the time of Cristobal de Olid's revolt in Honduras, I passed through the place with Cortes, and the majority of its inhabitants accompanied him also....

Thus it was that mother, son, and daughter came together, and it was easy enough to see from the strong resemblance between them that Doña Marina. and old lady were related. Both she and her son were very much afraid of Doña Marina; they feared that she had sent for them to put them to death, and they wept.

When Doña Marina saw her mother and half-brother in tears, she comforted them, saying that they need have no fear. She told her mother that when they handed her over to the men from Xicalango, they had not known what they were doing. She pardoned the old woman, and gave them many golden jewels and some clothes....

Doña Marina knew the language of Coatzacoalcos, which is that of Mexico, and she knew the Tabascan language also. This language is common to Tabasco and Yucatan, and Jeronimo de Aguilar spoke it also. These two understood one another well, and Aguilar translated into Castilian [Spanish] for Cortes.

This was the great beginning of our conquests, and thus, praise be to God, all things prospered with us. I have made a point of telling this story, because without Doña Marina we could not have understood the language of New Spain and Mexico.