(Cover) - EN Showbiz - Ryan Phillippe and Demi Lovato have been dating despite their 18-year age gap, according to reports.

The 36-year-old Hollywood actor has been dating the Disney star for the past few months, according to sources.

Demi, 18, is said to have been enjoying a low-key relationship with the father-of-three, but it has cooled in the last couple of weeks after his former girlfriend Alexis Knapp gave birth to his daughter, Kai.

"It was really hot and heavy for a while," a source told E! Online.

Demi was unsure if Ryan was definitely going to be a father again "until it basically happened" and added that it "threw her for a loop".

Ryan was married to Reese Witherspoon for seven years and shares custody of their two children Ava, 11, and Deacon, seven.

He is said to have been unsure if Alexis's baby was his initially but appears to be taking full parental responsibility and was there for the birth.

Demi is getting her singing and acting career back on track after spending two months in rehab earlier this year for her battle with an eating disorder. (C) Cover Media