She is the glamorous movie star who hired a nanny to teach her children the language of heaven in Hollywood.
But a new survey shows Swansea-born Catherine Zeta Jones is typical of Welsh-speaking mams - who are more likely than dads to pass on the language.
After the birth of Dylan, now five, Ms Jones, 36, said she was determined her son would learn about his Welsh roots.
However, the survey shows Welsh-speaking dads are far less likely to pass on their language to their young ones after tying the knot with a non-speaker, despite considering themselves much more fluent than women.
The new research also shows they are more likely to chat in Welsh to their mates and neighbours than their families.
The 2004 Welsh-language use survey found 90 per cent of children were fluent in homes where both parents spoke Welsh.
Fluency rates dipped to 64 per cent in homes where the language was only spoken by the mother. But in households where only dads spoke Welsh, just 54 per cent of children were fluent.
Gruff Hughes, general secretary of Welsh-medium teachers' union UCAC, said the figures proved women still rule the roost.
"My son is typical. He married a non-Welsh speaker, works full-time, and English is spoken in the house. I suppose that's why they call it the mother-tongue."
The Welsh Language Board (WLB) carried out the Assembly government-funded research over three years. Researchers found 21.7 per cent of children aged three to 15 could speak some Welsh in 2004-5, compared with 20.8 per cent recorded in the 2001 census. And in south-east Wales, the number of school-age Welsh speakers is now higher than in 2001.
But fluency across the country is falling, particularly in the traditional heartlands of the north and west. Earlier this year, TES Cymru reported that more pupils previously assessed as first-language speakers were being entered for the easier second-language Welsh GCSE, to boost results.
Latest figures from the survey reveal that, in 2004, 19.5 per cent of seven-year-olds were assessed in Welsh first language. But by age 11, the figure had dropped to 18.1 per cent, and to 14.5 per cent by age 14.
The WLB welcomed the figures showing more people are speaking Welsh. But chief executive Meirion Prys Jones said there needed to be more opportunities to speak it on a daily basis.
LOOK WHO'S TALKING
* Only 44 per cent of young Welsh speakers aged three to 15 are fluent compared with 72 per cent aged over 65.
* Children who are not taught Welsh at home are 50 per cent less likely to become fluent.
* The percentage of fluent speakers in the south-east - with 44 per cent of speakers in the three to 15 age group - has increased by 8.9 per cent. In Powys and west Glamorgan it fell by 11.1 per cent.
* Just over a fifth of fluent Welsh speakers speak Welsh when shopping or travelling on a bus.
* Two-fifths of Welsh speakers in the private sector said their employers supported their use of the language in the work place.