Estela de Carlotto, president of Grandmothers of Plaza de Mayo, right, and her grandson Ignacio Hurban pose for cameras at news conference in Buenos Aires, Argentina. (AP Photo/Natacha Pisarenko)

Buenos Aires - An Argentine man who recently learned he was the long-lost grandson of an activist who fights to find babies stolen during the 1976-1983 dictatorship posted a picture of them Friday on Twitter.

The picture, the first public image of them together, shows Ignacio Hurban, a 36-year-old jazz musician, with his arm around his grandmother Estela Carlotto, the president of the Grandmothers of the Plaza de Mayo rights group.

“Thank you. Thank you very much,” says the post.

Hurban - whose mother in fact named him Guido Montoya Carlotto, according to survivors of the secret prison where he was born - learned this week through DNA testing that he is the son of Carlotto's daughter Laura, a political prisoner killed by the military regime.

He met Carlotto, the 83-year-old activist known as “Argentina's most famous grandmother,” for the first time on Wednesday.

He has not spoken publicly since the discovery, but will give a press conference alongside his family at the headquarters of his grandmother's rights group in Buenos Aires on Friday afternoon.

Hurban's other grandmother, 91-year-old Hortensia Ardua, will also be at the event.

The two grandmothers, who did not know their children were a couple and have not yet met, described the intense emotions of the past several days in a joint phone interview with Radio Del Plata on Friday.

“When I used to see Estela, I would dream of one day finding my grandson,” said Ardua, describing how she used to watch Carlotto in the media and wish for her, too, to find her grandson.

“Now I understand why my daughter fell in love with your son,” Carlotto warmly replied.

A judge has opened an investigation to determine how Hurban ended up being raised by a family in the countryside after being taken from his mother at birth.

An estimated 500 children were taken from their imprisoned parents during the military regime's “dirty war” against leftist opponents. Hurban is the 114th to be found.

An estimated 30 000 people were killed or abducted and presumed killed during the dictatorship.