Clooney's first cousin, NCIS: Los Angeles actor Miguel Ferrer, says he plans to attend the nuptials.
"I don't know if I can tell you a lot about this marriage," Ferrer, 59, told France's Tele Star magazine during the Monte Carlo Television Festival, which wrapped in Monaco yesterday.
But, he added, "Obviously I'll be there!"
A source close to Alamuddin's family told PEOPLE last month that the couple plan to tie the knot in Italy in September.
Ferrer is the oldest of five children of Oscar-winning actor José Ferrer and famed singer Rosemary Clooney. Rosemary's brother, Nick, is George's father.
Although he was tight-lipped about details of the big day, Ferrer did open up a little about his cousin's new fiancée.
"At first the family was surprised to learn the happy [engagement] news," he said, adding that since the proposal he has come to know the British lawyer as "a wonderful woman."