Lindsay Lohan and Samantha Ronson shopping on Melrose Avenue on December 24, 2008, after allegedly having a big fight in the morning.  [CFP]

On Tuesday Lindsay Lohan revealed on her MySpace blog, "My father just let my family and I know, amongst others that he had another child after my little sister Aliana, or maybe he had it before Aliana??"

”He cheated on my mother and that really sucks … MERRY CHRISTMAS!!!," the actress, 22, wrote a blog post titled "Random Thoughts." .

But in a rebuttal e-mail sent to People Magazine, the star's controversy-plagued father Michael Lohan is refuting the claim. In fact, he thinks the entry was penned not by his daughter, but by her DJ gal pal Samantha Ronson.

Related readings:  Samantha Ronson depressed claims Man arrested for grabbing Lindsay Lohan  Lindsay Lohan: MySpace will be first place to know about spilt with Samantha  Lindsay Lohan's strong love

Reports that Michael Lohan, father of Michael, Lindsay, Ali and Cody Lohan, might have had an illegitimate child surfaced in June when a woman named Kristi Horn claimed that she'd had a daughter by him 13 years ago.

"Why would someone without taking a test put something out there like this? What if it's negative?" Lohan said in June in interviews with the Associated Press.

On her MySpace blog, Lohan sends her love to all of her family members except her father. She also reveals that she'll be spending the holidays with her girlfriend in LA.

"I love my Mom, Aliana, Cody, Michael, and my Nana Sullivan!! I will be missing them this Christmas as it is the first one I am spending away from home. I am spending it with Samantha in Los Angeles."