Yes. I could tell in that picture. Sometimes good couples are when two weird people come together and be weird togteher. They both look like light hearted practical joking people. They look like people who are in sync and who could find each other in a crowd of people. The more similar they are (looks, behaviour etc) the more apparent this is in my opinion
My brother and I are often mistaken for a couple when we hang out together. We're not really sure why, aside from the fact that we're around the same age and height, and we get along pretty well obviously.
So I try not to assume anyone is together, unless I'm told otherwise or I notice some PDA.