What about siblings?
good friends of ours own Simbas brother, they used to have 'playdates' lol, we would bring them over (simba went there, as a kitten), and just watch them play. it basically stopped when they got fixed and couldnt have them all hyper.
A while ago... his brother scooted outside (they live next door), he never runs, just kinda scoots out and looks. Well, they picked him up just for fun and held him up to our open (with a screen) window.
We jokingly said "call your brother", and boom, there was Simba! But, no anger or territory stuff was present at all. i think simba was curious, he meowed at him (which he never does), and looked for him even after butterscotch went inside. Butterscotch was a bit scared/out of his element.... but... nobody was dominant.
Do you suppose they remembered they are brothers? we havent tried indoors at all. simba is such a scardey cat now, and same with butterscotch kind of... so we didnt want to scare them on purpose. That day at the window really got me thinking!