Natural occurance of triplets its estimated at about 1 in 8000 (I'm rounding) and quads is about 1 in 700,000, quints 1 in 55 million. So possible but unlikely

Only surviving natural quints I've heard about was the Dionne quints back in the 1930s. They were identical - very rare. Here's a link to a family that had natural quads
http://www.dixonquads.com . I think they started as quints but one was lost.