In an exclusive report to OK! Magazine Friday, Michael Lohan confirmed that while separated from his ex-wife Dina Lohan, the "Bossy" singer's mother, he had a romantic relationship with another woman which resulted in the birth of a baby girl.
"Years later (the woman) contacted me, convincing me that I was the only person she was with and that she had my child," he said of the child and her mother.
In addition to the "Mean Girls" actress, Michael and Dina Lohan had three other children before their divorce in 2007.
The New York Daily News reported that Michael Lohan previously denied having a child with the woman, who he identified as Christy Horn, and is prepared to take a paternity test.
Lohan has also questioned why news of the 13-year-old child came about while his daughter is enjoying a successful music and film career, the News said.
"Why did she come forward now?" he said of Horn. "Is it because Lindsay is a big star? Is she looking for money?"