Although we got a quick peek at them back in May, singer/songwriters Elvis Costello, 53, and Diana Krall, 42, officially introduce their fraternal twin sons in this week's issue of People magazine. Dexter Henry Lorcan and Frank Harlan James made their debuts on December 6th, 2006, and are now 9 months old.

Click below for the photos and interview highlights.

(Diana with Dexter, above.)

Diana may refer to her twin sons as 'lovely, funny, good boys' but they're also known by another nickname -- her 'carny kids.' Starting when they were 6-months-old, the boys joined mom for a three month tour in promotion of The Very Best of Diana Krall. On the tour bus, equipped with two cribs left over from the Dixie Chicks and their brood, Diana got a little crazy with some classic children's songs. She jokes,

I'm practicing the smoky, sexy, Scotch-infused tones of 'The Wheels on the Bus.' The wheels on the bus went round and round and round for, like, 18 hours a day [while we were on the road].

While the boys enjoy mashed papaya and salmon (two favorites), Diana and Elvis tend to keep everything other than food laid-back and low-key.

There's this book I picked up in England called something like, 'A Healthy, Calm, Content Household with Twins.' It's like, 7 am, open up the curtains, feed them, 11 am, close the curtains, put them in their beds...You need a whistle and a stopwatch!

Diana reveals that she is back to her pre-pregnancy form thanks to cutting out sugar and dairy and practicing yoga. She also credits her sons:

I'm lifting 22 lbs babies all day!

(Elvis with Frank, above.)

Elvis likes to play songs for the boys on his guitar, and between that and being on tour, Diana thinks Dexter and Frank may have picked something up -- applauding their parents.

If we just walk into the room, they start clapping. We didn't train them to do that for applause!

Diana reveals a pet-peeve that is the bane of many a mommy's existence -- the high-pitched squeaky voices emitted from many infant toys. However, Diana has a solution.

I think I'm going to audition for Fisher-Price, so parents just don't go mental.

Source: People, October 8th issue, p. 114-115