Acting President Raul Castro sat in for his ailing brother Fidel on Wednesday at an event marking Elian Gonzalez's 13th birthday — and another year of the ideological campaign launched after an international custody battle over the Cuban boy.

Raul Castro, 75, has been increasingly taking on his brother's public duties amid persistent questions about when — or if — Fidel Castro will return to power.

Dressed in his habitual olive-green uniform, Raul Castro sat in the front row of the auditorium in Elian's hometown of Cardenas, a coastal city about 85 miles (140 kilometers) east of Havana, for the gathering that featured a children's choir and dance troupe.

"Our greatest challenge is to strengthen and enrich the immense work of the revolution," Communist Party leader Mercedes Lopez said in a brief speech at the hour-long event.

The younger Castro, who is also the island's defense minister, did not address the gathering.

Fidel Castro has not been seen in public in the more than four months since he provisionally ceded his powers to his brother after undergoing emergency intestinal surgery. He did not show up for five days of delayed 80th birthday celebrations culminating Saturday in a major military parade.

Official photos and videos of the ailing leader have been released occasionally — the last one more than a month ago — and his medical condition remains a state secret.

In past years, it has been Fidel Castro who has traditionally attended the annual birthday celebrations for the boy who was just 5 when a pair of fishermen found him floating on an inner tube in the ocean off Florida's southern coast.

Now a teenager, Elian remains a living symbol of Castro's victory in the high-profile seven-month battle against his enemies in exile over where the boy should live — with his father in Communist Cuba or with his great-uncle in capitalist Miami.

He remains a household name on the island, where his face was emblazoned on T-shirts and posters during the ideological battle for his return to Cuba. Although he is said to live as normal a life as possible in his hometown, the boy is still seen with his family at major political events several times a year.

Elian reportedly refers to the leader as "Grandfather Fidel" and sent a get-well card that was published in state media after the man who ruled Cuba for 47 years suddenly fell ill in July.

Elian attended Wednesday's event, along with his father Juan Miguel Gonzalez, his stepmother and his two half brothers.

Elian's parents were divorced when his mother decided to take the boy on her journey by boat to the United States. She perished after their boat, filled with a dozen would-be migrants, capsized in a storm in November 1999. Elian was among three survivors.

A high-profile custody battle between Elian's relatives in Miami and his father in Cuba ensued. Beginning in December 1999, hundreds of thousands of Cubans took to the streets in a government-led campaign to demand Elian's return to the island.

The battle ended with Elian's dramatic seizure by armed U.S. federal agents from the home of his Miami relatives on April 22, 2000. The boy returned to Cuba with his father that summer.