Asterix creator Albert Uderzo has said he is to sue his daughter and son-in-law for "psychological violence", his lawyer says.
A rift has pitted father against daughter Sylvie since 2007 over the Asterix legacy.
She says that, by selling his 60% stake in the Asterix publisher in 2008, her father allowed the series to continue after he dies, betraying its spirit.
She filed a legal claim in 2011, saying her father was being exploited.
That claim against persons unknown for "abuse of fragility" is soon expected to be dismissed by judges, although Ms Uderzo is likely to appeal, reports say.
Mr Uderzo, 86, has been declared mentally fit during the course of the investigation, Le Point magazine reports.
His daughter had accused "people around him" of taking advantage of his age to influence the management of his work and his money.
But Mr Uderzo says he is not in a "state of fragility" and has instead been the victim of harassment. He accuses his son-in-law, Bernard Boyer de Choisy, of being behind various legal moves by his daughter against him.
"We have decided to let Sylvie Uderzo and her husband understand that we will not let it go," said lawyer Pierre Cornut-Gentil on Monday.
The rift goes back to 2007 when Ms Uderzo and Mr de Choisy were dismissed by Asterix publisher Editions Albert Rene as managers of the Uderzo estate.
The 35 albums in the Asterix series have sold more than 352 million copies around the world and have been translated into more than 100 languages.
The latest offering in the series, Asterix and the Picts, was published in October in 15 countries and 23 languages by new author Jean-Yves Ferri and illustrator Didier Conrad - the first people, other than original creators Uderzo and late author Rene Goscinny, to produce an Asterix story.