Denise - who has daughters Sam, eight, and Lola, seven, with Charlie, as well as adopted Eloise, 18 months - said: "[The twins] are back with Brooke Mueller.
"This is not the first time I've had all five, they're Sam and Lola's brothers. It was a full house, lots of love and life. Brooke knows anytime, and Charlie, that any time they need help with the boys, that I'm there."
Denise - who was married to Charlie from 2002 to 2006 - is aware people see the set-up as "unconventional" but she would never turn her back on the little boys because of how much they mean to her daughters.
She added to 'Access Hollywood': "They're our family and they're Sam and Lola's brothers and I can't imagine growing up without my sister, so anytime she needs help, I'm there for the boys.
"[Sam and Lola] are the best big sisters to [the boys] and they love them.
"I know it doesn't seem normal, but it is our normal. They're little kids and I love children, and like I said, it's our daughter's brothers, so I can't say no."