Actress Gabrielle Union was stunned when Dwyane Wade asked her to marry him - because she did not think he was serious about getting married.

The U.S. basketball star popped the question in December (13) with an elaborate proposal involving his two sons, but the Bad Boys Ii star did not take the romantic gesture seriously at first, because the kids have asked her several times in the past if she would be their stepmum.

She tells U.S. breakfast show Live! with Kelly and Michael, "I was completely surprised, him and the boys planned it completely as a family. We were just going to spend the day together, have a little bit of quality time... I'm completely clueless.

"(Dwyane's) like, 'Do you want to do any make-up?' I'm like, 'No.' So my nails aren't done. We were literally going from (brunch) to our house, that is under construction, so I'm dressed to go to a construction site, not for anything exciting.

"So we do a little tour of the house. Me and (Dwyane) are upstairs, the boys are downstairs and the boys say, 'We want to do a presentation for you'. I thought they were going to do a skit or a song or something, so me and (Dwyane) turn around... and they're holding signs saying, 'Will you marry us?'

"I was like, 'Aww,' but the thing is they ask me all the time. So I was like, 'This is embarrassing, now they've made signs.' I turned to (Dwyane) and he's down on one knee and he's like, 'Will you marry us?' and I'm like, 'Oh, you're serious,' and I'm like, 'Of course,' but the kids couldn't hear me and they think I'm saying no... and I'm like, 'No, no, yes,' and they tear up the stairs (to congratulate us)."

The engagement news preceded reports Wade had fathered a child with another woman while he and Union were on a break.

Wade has responded to the reports, calling his new son a "blessing". Union has yet to comment on the baby news.