Dennis Quaid believes prayers saved the lives of his twins.

The 56-year-old actor's now two-year-old twins Thomas Boone and Zoe Grace were just two weeks old when they received an accidental overdose of the anti-coagulant drug Heparin in 2007, and Dennis is convinced a "higher power" saved them from dying.

He said: "A lot of people told us later that they were praying for our babies. In the end, I believe that the power of prayer from so many is what saved them. It's so obvious to me that a higher power in the universe is controlling what's going on.

"I thought, 'They're 12 days old, and they're going to change the world.'

"They're really tough, and they should be proud. Because of what happened to them, they already saved lives. This is their legacy."

The 'Pandorum' star admits he and his wife Kimberly Buffington - who had the twins via a surrogate mother - felt totally helpless as they watched their 12-day-old children be treated at Los Angeles' Cedars-Sinai Medical Center.

In an interview with the September/October issue of AARP The Magazine, he added: "We could see them [Cedars Sinai medical staff] working on the kids. It was chilling. Initially, I felt this really couldn't be happening. Then I felt fear - and helplessness. They were really in a lot of discomfort, crying. It had to be painful."

Thomas Boone and Zoe Grace were mistakenly administered with 10,000 units of Heparin, rather than the 10 units babies are allowed, when medical staff carried out treatment for staph infections.

In 2009, the couple received $500,000 from Los Angeles' Cedars-Sinai Medical Center, as well as an agreement the hospital will provide future medical care for the twins if they suffer from any condition related to the accidental overdose.