My boys:
Sparkles- 5-6 year old grumpy VT- Flares at everything and anything.
Zues- Young Super Delta- Only ever seen him flare 2 times I think at his reflection. He was SOOO beautiful- Wont even flare for the Mirror
Pandora-Young Cambodian Delta- Ive only had for a few weeks and will flare only at the mirror
Tika- Young Crowntail- Ive only had for a few weeks but doesn't flare expect when peeking through the front of the divider at Pandora.
They can't see eachother through the divider only in the small space at the front and back because its black otherwise they would be flaring all day I would imagine.