Daughter of Tiberius Sempronius Gracchus and sister of the famed brothers Gracchi, Sempronia married her cousin Scipio Africanus Minor around age 17.
When Scipio Africanus Minor discovered that his cousin and step-brother, Tiberius Gracchus, then Tribune of the Plebs, was undermining the established order, he encouraged Gracchus' enemies, especially their mutual cousin, Scipio Nasica.
In 133 BCE a group of senatorial soldiers, led by Scipio Nasica clubbed Tiberius Gracchus to death on the steps of the Capitol along with some of his followers.
Scipio Africanus publicly condoned the murder, and even though he had not yet returned from Spain, he was often credited with the deed. Indeed, after his return to Rome he was publicly asked by the tribune C. Papirius Carbo what he thought of the fate of Gracchus, and replied that he was justly slain.
Soon afterwards, in 129 BCE—in fact, on the very morning of the day on which he had planned to make a speech referencing the agrarian proposals of the Gracchi, he was found dead in bed. Rumours flew that he had been murdered, and the Cicero notes that the first suspect was his wife, Sempronia.
The mystery of his death was never cleared up, but it is just as probable that that he was assassinated by one of the supporters of the Gracchi, probably Papirius Carbo his bitterest enemy, who Cicero named as the guilty party, though doubtless he was granted access to Scipio's wife by Sempronia, faithful to the memory of her brother.