There are supporting characters who are definitely not portrayed as children. Elmo, for example, has a mother and a father, and a set of grandparents. These are not children.
Does this mean Bert and Ernie are doing a cover of the equal rights song from Popstar: Never Stop Never Stopping? 
The thing is, Bert and Ernie are based on Jim Henson and Frank Oz’s real-life relationship. So of course Frank Oz doesn’t think they’re a gay couple, because he was Henson’s collaborator, not his forbidden lover.
Anyway, just because you’re the creator of a fiction that doesn’t mean you’re the best person to understand your own fiction. Sometimes stuff that the creator can’t acknowledge consciously comes bubbling out in sublimated form. But sometimes a cigar is just a cigar.
Sesame Street has shown many families of Muppets over the years. Parents, kids, etc. How did these kids get produced* in that world then?
Bert and Ernie could be a family as well. (But clearly they are just roommates.)
Again, a blanket denial on Muppets’ sexual orientation on *SS *just doesn’t work.
- Well, not counting someone with scissors, cloth, needle and thread.
If you don’t want to hear that Bert and Ernie aren’t gay, then stop asking.
Imo it’s really weird that people want to know sexual orientation of puppets on a show for literal babies.