That's what I was thinking. But from what I understand, there was only 1 female and no male ornate box turtles in the home this little guy is coming from. I am pretty sure all the species were mixed in one big indoor enclosure and many random eggs all the time. Maybe they have a male box turtle and don't realize it.
Box turtles and Tortoises can't hybridize, that would be like a dog and a cat having a litter, and yes box turtles can store sperm up to 5 years.. Nice looking ornate box turtle, congratulations!