San Antonio Mayor Julian Castro, a rising star in the Democratic party, will have his chance to shine in prime time Tuesday as the first Latino to deliver the keynote address at his party's national convention.

The 37-year-old twin won in a landslide re-election last year and speculation about whether he'll become the governor of Texas or even the country's first Hispanic president.

What hints Julian Castro has dropped about his speech suggest a script heavy on a defense of President Barack Obama's record along with a telling of the story of how he and his identical twin brother, Joaquin, grew up, raised by a single mother. Joaquin, a Texas state legislator now representing San Antonio and poised to win election to Congress in November, will introduce his brother at the convention opener Tuesday night.

Some would say the mayor has had a swift and charmed ascent. But his mother, whose own political activism on behalf of Hispanics when her boys were young drew hate mail and, she says, the attention of the Justice Department, knows her sons' rise is evidence of Hispanics' growing and long overdue political power.

"They called us militant, but our way of doing things was through political ends," Rosie Castro said of her fight for Mexican-American rights in the 1970s. "Not through guns, not through overthrowing the government, but through the political process."

How the twins even wound up in elected office is a debt owed to their mother. Now 65, Rosie Castro is the protagonist of the family story the mayor says he'll tell a national audience. A civil rights activist and single parent from the time the twins were 8, she dragged the boys to rallies and often argued politics with them.

Julian Castro says he knows his mother's generation faced different burdens than the Hispanics he's trying to connect with today, and he credits her civil rights work with laying the ground work for his political success.

"It was very warranted at that time," the mayor said. "You had a huge dropout rate. You had signs that said, 'No Mexicans or dogs allowed.' It was a movement born out of both aspiration and frustration. It was very understandable. And ultimately, I believe, helped move this country forward."

Rosie Castro made a failed run for San Antonio city council when she was 23 but quickly found her calling as a political organizer in Texas' Mexican-American community in the 1970s. She didn't reap the fanfare enjoyed by her sons.

Sitting in a downtown Mexican restaurant before leaving for the convention, Rosie Castro ticked off the costs of her activism: harassing phone calls in the middle of the night and packages sent to her house calling her communist. She says authorities kept close tabs on her organizing efforts, and a local newspaper branded her as militant.

"I don't know that I was terrified, but it left me unsettled, especially since my sons were children," she said of the mail and late-night calls. "I don't know if there was a nut that would do anything."

At one point, Rosie Castro said, her activism kept her from jobs in the city government office her son now runs.

Now Julian Castro is at the forefront of his party's effort to attract Hispanic voters, just as his mother had labored to register them to vote nearly 40 years ago. To Rosie Castro, the strides made in the span of just one generation don't seem to have come quickly.

On the eve of his keynote speech, the mayor told reporters in Charlotte that he hopes his life's story will inspire younger Hispanics.

"As my family story shows, Latinos have been a blessing for USA for many generations," Julian Castro said. "The future of America depends in part on the success of the Latino community, and this opportunity is just one more signifier of that."

Based on reporting by the Associated Press.

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