Bec and Lleyton Hewitt were thrilled to be back on home soil for their daughter Mia’s 7th birthday, with grandparents and cousins there to join in the fun. For Bec, the celebration was made even more special, with older sister and look-alike Kristy on hand for the laid-back family gathering.

“Bec and Kristy are incredibly close and always have been,” an insider tells Woman’s Day. “Their bond is not affected at all by Bec living overseas [in the Bahamas since 2009].” The friend adds that Kristy has long been Bec’s confidante. “She’s the closest friend Bec has – a very sweet person – and she was a dancer and singer from childhood, so they share plenty.”

In fact, says the insider, “Kristy is one reason Bec was so keen to have a third child – she wanted to give Mia a sister, the friend for life she has in her sister.” Lleyton also gets along famously with his down-to-earth sister-in-law.

“Bec’s other close friends are actresses or in the entertainment industry, [whereas with Kristy] Lleyton knows she isn’t trying to put the stars back in Bec’s eyes and take her focus away from the family. Kristy is very much a homebody like Bec and is happiest surrounded by kids.”

See more pics of Bec and her sister and find out how Mia celebrated her birthday in this week's Woman’s Day on sale Monday January 28, 2013.