Hi, so I've seen the red wedding mentioned in game of thrones and venom 2. Yes, I can smell you judging me from here! It's okay.
I was just wondering if this is a recent myth? Where does the red wedding concept come from?

There are a number of incidents in world history, some verifiable, some dubious, of similar massacres during events of hospitality. Vlad the Impaler of Romania supposedly murdered many of the unruly noble vassals of Transylvania after inviting them to a feast, for example. Genghis Khan's father, Yesugei, was poisoned at a wedding feast, when Genghis was just a young boy.

In general, most rulers prefer to avoid violations of hospitality because this leads to an atmosphere of fear that makes negotiation nearly impossible, and negotiation is the foundation of both explicit truces and implicit peace outside of wartime.

One example I know of happened during a feast, not a wedding, where the host killed the guests which lead to a revolt.

From wikipedia entry of Gero:

In 939, an Obodrite attack left a Saxon army routed and its margravial leader dead. Gero in revenge invited thirty Slav chieftains to a banquet whereat he killed all but one, who managed to escape by accident. In response, the Stodorani revolted against German overlordship and chased the Germans across the Elbe, but Gero was able to reverse this before Otto's arrival in Magdeburg later in the year.