NFL's Martellus Bennett thinks children's books need more black stars. So he wrote his own.

Martellus Bennett had already noticed the problem. But it was put into sharp focus after his daughter, Austyn Jett, was born two years ago. 

"There aren't many children's books about black characters that are just going on adventures," the NFL star told Mashable this month. Black characters, he found, tend to star in children's books with directly racial themes. "My library has over 2,000 children's books in it, and most of the protagonists are either white or creatures."

So Bennett did something unusual -- he wrote a children's book with a black protagonist named AJ, based on his own daughter. The first story, called Hey AJ, It's Saturday, comes out Father's Day weekend. A series will follow. 

Surprised? You shouldn't be. This is Martellus Bennett, after all.

Bennett is 29 years old and among the NFL's most talented tight ends. He made the Pro Bowl in 2015, and signed with the New England Patriots this spring. But he's also among the league's more colorful characters, a man with interests that range well beyond football. 

ESPN once describe Bennett as "an artist, illustrator, writer, fashionista, musician, director, composer, CEO and, oh, about 87 other things."

Take the shelf that houses part of his massive book collection, for example. Bennett designed it himself, and shared a photo on Instagram earlier this year. 

Hey AJ, It's Saturday follows our protagonist on a weekend morning. AJ's parents are sleeping in. She decides to go into the kitchen and -- well, you'll have to read the book to find out. 

"She's super curious -- I think curiosity is one of the most important traits a human being can have," Bennett said. "Saturday was one of my favorite days as a kid and I think the best way to get to know a kid is by what they do on a Saturday morning, so that's how I wanted to introduce AJ to the world." 

Two more stories starring AJ are planned for next year, and an app will accompany all three books. But that's just the beginning. 

Original image has been replaced. Credit: Mashable

Bennett has schemes on an AJ cartoon series, too, and says New York Jets running back Matt Forte will voice her dad. He also wants to make another cartoon series, not related to football but voiced entirely by current and former NFL players. To manage those projects and others, he's launching The Imagination Agency, what he calls a "multimedia production" outfit.  

"I've always wanted to create," he said. "I didn't ever want to just be a football player, so I'm just bringing all these childhood dreams together to try to accomplish the things I want to do before I die." 

Original image has been replaced. Credit: Mashable

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