Ok so Jared and Stephen Amell became friends sometime around 2014, and between 2014-2016 they were interecting on social media pretty much constantly, and often hanging out together, and they were always playing up the flirty stuff together, like constantly.

Check out @sunflowerchester's amellecki tag if you want a good record of their interections - very fun times.

Anyways Jensen's jealousy of Amellecki is one of those things that was partly exagerated by the fandom because it was so fun haha, but also definetly based in reality, with a dose of Jensen doing his over the top grumpy act about it.

A few instances below - there were definetly more interections between them on Twitter where they played up the rivals for Jared's affection thing (but Stephen's twitter doesn't exist anymore so its hard to track down) and more times when he was brought up at cons and Jensen would get all grumpy about it.

Probably one of the most infamous incidents is that this well-known Jensen tweet:

Was made just hours after this interaction between Stephen and Jared and let's just say it felt VERY pointed lmao

Hense this post lol

Examples https://www.tumblr.com/peanutbutterandbananasandwichs/777976688332193792?source=share