Relighting a candle by igniting the smoke. The smoke contains unburned wax vapor.
What if the Bros have a S/O who's a theater/musical actor/actress but didn't tell the bro and the bros walk in on their S/O with a costar doing something that would make them jealous/mad/upset? Like the S/O is practicing lines about leaving the bro or grinding on the costar or french kissing. Maybe a different one for each bro too? And it could end in fluff or nsfw, if ya know what i mean ;) ;)