Bert and Ernie are best friends. They were created to teach preschoolers that people can be good friends with those who are very different from themselves. Even though they are identified as male characters and possess many human traits and characteristics (as most Sesame Street Muppets™ do), they remain puppets, and do not have a sexual orientation.
Dang. That’s too bad. The one thing missing that would have softened the blow is “not that there’s anything wrong with that.”