The 37-year-old "Avatar" actress said on a talk show that she and husband Marco Perego have been enduring since trying to sleep train their boys, explaining that twins means double the trouble.
Ruffalo, 47, as a father of three said he suggested her that she should "just forget it" it's not worth stressing about, reported E! Online.
"Let them come in your bed and slowly transition them out," he said.
Ruffalo also said that trying to force children to sleep in their own bed could cause "major problems.