Although Robert Alda was regarded as a devout Catholic when he was married and when his wife gave birth to their only son together (Alan Alda), Robert Alda nevertheless defied Church strictures and left his wife. Robert Alda divorce Joan Browne while his son Alan Alda was still growing up, and soon thereafter he married Flora Martino.
Alan Alda continued to have close relationships with both parents, but the experience of seeing his ostensibly devout Catholic parents get divorced apparently had a strong impact on him. As an adult, when Alan Alda married he did so only once: forging one of the most famously strong, life-long marriages in all Hollywood history.
Robert Alda remained married to his second wife, Flora, until he died on 3 May 1986. Robert Alda and Flora had one son together: Antony Alda, film and television actor like his half-brother (although considerably less famous).
From: Raymond Strait, Alan Alda: A Biography, St. Martin's Press: New York, NY (1983), page 9:
 The handsome young [Robert] Alda was undaunted by national gloom or unstable economic news. He pursued his newfound [stage acting and comedy] career with great diligence and determination, taking whatever problems he and his wife might have to mass on Sunday mornings and leaving them there. Like his parents, he was a devout Catholic with deep religious convictions.The birth of Alan Alda, to Joan and Robert Alda, who were devout Catholics, from: Strait, pages 10-11:
On January 28, 1936... Joan Alda went into labor. After many hours, an exhausted Joan Alda finally gave birth to a son (their only child), who was given the shortened name of Alan (from Alfonso) and immediately became known to one and all as "Allie," a name that sticks with him even today.
Barely twenty-one years old himself, [Robert] Alda had very little to offer his new son [Alan Alda] other than love and a roof over his head. He continued to work in the Catskills and around New York City, but nothing sensational was happening, although he never missed a chance to better himself. He wanted more than burlesque. During the summertime when work was slow, he would play in stock--which was becoming more important on the Borscht Circuit. Looking toward Broadway, he talked with agents and pitched his best side... In 1937, he [Robert Alda] had the distinction of being one of the first performers on television.