Julian Castro, mayor of San Antonio, left, waves while on stage with his brother, Rep. Joaquin Castro (D-Texas), at the Democratic National Convention last year. (Photo by Daniel Acker/Bloomberg)

The Maryland Democratic Party has booked Rep. Joaquin Castro (D-Tex.), a rising national political star, as its guest speaker at an annual gala next month.

The planned appearance comes amid a busy stretch for both the congressman and his twin 38-year-old brother, Julian Castro, the mayor of San Antonio. The mayor was the keynote speaker at last year’s Democratic National Convention.

A story published by Politico on Thursday detailed the emergence of the Castro brothers on the Democratic party speaking circuit, reporting that by the end of October, they will have appeared at major functions in at least 11 states outside their native Texas.

The Maryland Democrat gala, an annual fundraiser, is scheduled for Sept. 12 in Greenbelt. Tickets start at $250.

Yvette Lewis, chairwoman of the Maryland Democratic Party, said that Joaquin Castro, a second-generation Mexican American, is “a proven champion for those striving to pursue the American Dream.”

“His work on critical issues like immigration reform serves to inspire us as a party for the battles to come,” Lewis said. “I not only look forward to hosting him here in Maryland, but to following his promising career as a public servant.”