Members of a prominent South American banking family filed a $612 million suit against Merrill Lynch & Co. claiming the investment bank inappropriately liquidated an account they maintained with it to cover losses Merrill research caused in another account.

In the complaint, Ezequiel Nasser, Raymond Nasser, Albert Nasser and others say they purchased options in investment bank Bear Stearns Cos. on the written advice of Merrill Lynch analysts.