Nearly half of American dads under 45 this Father's Day say they have at least one child who was born out of wedlock.

And the share of fathers living apart from children is more than double what it was just a few decades ago, according to a new study.

But among married fathers, children are said to be getting more attention from both parents at home than ever before.

A Pew Research Center report highlights the changing roles of parents as US marriage rates and traditional family households fall to historic lows.

The study found that college-educated men who tend to marry and get better jobs are more involved with their children than lesser-skilled men struggling to get by.

Pew's survey and analysis of US government data found that more than one in four fathers - 27 per cent - with children 18 or younger live away from at least one of their children. That number is more than double the share of fathers who lived apart from their children in 1960.

But married fathers who live with their children are actually devoting more time helping their wives with caregiving at home - a task once seen almost exclusively as a woman's duty. Such fathers on average now spend about 6.5 hours a week on child care, which include playing, helping children with homework or taking them to activities. That's up from 2.6 hours in the 1960s.

Among fathers with at least a bachelor's degree, only 13 percent had children outside marriage, compared to 51 percent of those with high school diplomas and 65 percent of those who didn't finish high school.

Age, too, was a factor. Three quarters of fathers who were 20 to 24 had children out of wedlock, compared to 36 percent for fathers aged 35 to 44.

The findings come as the latest US census data show that marriages have fallen to a record low, pushing the share of US households with married couples below 50 percent for the first time.

Sociologists say younger people are increasingly choosing to live together but delay marriage as they struggle to find work and resist making long-term commitments.

(Read by Lee Hannon. Lee Hannon is a journalist at the China Daily Website.)