Secretary of Housing and Urban Development Julian Castro introduces Democratic presidential candidate Hillary Clinton at a "Latinos for Hillary" grassroots event in San Antonio, Oct. 15, 2016. Getty Images

Politician brothers Julián and Joaquín Castro have reportedly started preparing just in case Democratic presidential front-runner Hillary Clinton selects one of them to be her running mate for the November general election. The Castro brothers, whose names have been floated for months as possible Clinton vp picks, are brushing up on their Spanish-language skills, according to a Sunday Page Six report.

Anonymous sources told the tabloid the Castros have been "cramming with Rosetta Stone" because, as a vice presidential nominee, either one would "have to be able to say a few phrases" in Spanish to secure Clinton's support among Latino voters. However, Julián Castro's spokesman told Page Six rumors of the study sessions weren't true.

The 42-year-old identical twins are second-generation Mexican-Americans, but neither is fluent in Spanish — an issue that's come up repeatedly as they've climbed the political ladder. This weekend wasn't even the first time reports of their Spanish studies have surfaced in the press.

In January, Politico wrote that Julián Castro, the former mayor of San Antonio and the current United States Secretary of Housing and Urban Development, had been "spending more time reading and watching television in Spanish, trying to get his speaking skills up to speed." The article followed a 2010 New York Times report that said he had a Spanish tutor.

Rep. Joaquín Castro, D-Texas, has denied getting help to learn the language, telling the Times in 2014 he understood Spanish "fairly well, unless somebody is speed-talking."

Whether they need Spanish to help Clinton remained unclear. Mexican-American lobbyist Larry Gonzalez told NBC News recently that criticism of Julián Castro's language chops was misinformed. "While yes, Spanish is helpful with certain audiences in certain parts of the country, it is his story and his family's story and their plan to help the Latino community — "their" being Hillary as a potential president and him as a potential vice president — that matter," Gonzalez said.

In a February poll released by the Washington Post and Univision, about half of Hispanic voters indicated they planned to vote Democrat, 14 percent said Republican and 32 percent were unsure. About two-thirds of respondents said they had a favorable opinion of Clinton. Meanwhile, only 16 percent said they had a favorable opinion of GOP front-runner Donald Trump.