Their sons Leo and Mike also entered the family business after making their own forays into children's publishing as an author and illustrator, respectively. In the 1990s, the men worked on the Berenstain Bears "Big Chapter Book" series (published under the names Stan and Jan Berenstain). Following Stan's death from lymphoma in 2005, Mike collaborated with his mother on writing and illustrating Berenstain Bears installments, while Leo has been involved with the business side of the franchise. Jan Berenstain died in February 2012 following a stroke. Mike Berenstain continues to write and illustrate new books in the series.