Kate Hudson has called Kurt Russell 'dad' for years, but her biological father exclusively tells RadarOnline.com it's "really painful" to hear his daughter refer to another man as her dad.

"At first it was okay when everybody was getting along, but there were certain things I didn't like. I didn't like that Goldie wanted the kids to call Kurt 'pa,'" Kate's father Bill Hudson told us in an exclusive interview.

"It was very confusing to the kids, particularly Kate, and that was really painful."

Goldie Hawn and daughter Kate Hudson are about to be exposed by someone who was once very close to them.

Goldie's ex-husband and father of Kate, Bill Hudson, has written a tell-all that will be released this fall and RadarOnline.com has obtained the cover of the book titled 2 Versions: The Other Side of Fame and Family.

Bill, 61, married Goldie in 1976 and the couple had Kate and brother Oliver Hudson together before divorcing in 1980, and the children were ultimately raised by Goldie's life partner, Kurt Russell, who she met shortly after her relationship with Bill ended.

These smokin’ hot stars manage to steam up the beach on their own, but when they bring along their equally sexy siblings, they scorch up the sand!

RadarOnline.com has photos of Hollywood's hottest brothers and sisters, stripped down and showing off their bombshell beach bodies, in the special photo feature.

Kim Kardashian has some of the most swerving curves on the shoreline, so when she teams up with her sexy sister Kourtney, the sexiness factor rises to the max.

Kate Hudson's estranged dad, the ex-husband of superstar Goldie Hawn, is lashing out at his daughter with the stinging claim that the actress is refusing to visit her dying grandmother.

PHOTOS: Kate Hudson Shows Off New Sexy Curves

Speaking exclusively to RadarOnline.com, Bill Hudson has accused the pregnant How to Lose a Guy in Ten Days star of neglecting her 88-year-old grandma, who is battling Alzheimer's disease.