Ronan Farrow, the 24-year-old son of Woody Allen and actress Mia Farrow, took aim at his dad on Father's Day on Twitter.
"Happy father's day -- or as they call it in my family, happy brother-in-law's day," he tweeted Sunday.
Mia Farrow retweeted the message and said "Boom."
The tweet started to circulate massively on the micro blogging site and even was dubbed "Tweet of the Year" (by Jemima Kahn).
Allen left Mia Farrow in 1992 and married her adopted daughter Soon Yi Previn, in 1997. Since he left Farrow, Ronan and Allen have reportedly been estranged.
Ronan, a human rights activist who serves as special adviser to the Secretary of State for Global Youth Issues, is widely quoted as disparaging Allen and having said he cannot see him.
He has said before about the relationship: "He's my father married to my sister. That makes me his son and his brother-in-law. That is such a moral transgression."
The relationship became a scandal, Allen was 56 and Previn was 21 when it started.
Now they have two adopted daughters, Bechet and Manzie Tio.