It Runs in the Family
The entirety of Young Justice, the Justice League and the Teen Titans along with the other teams are invited to a huge event to celebrate the ten year anniversary of the Justice League. However, this also means that the entire Bat-Family, Arrow-Family, Super-Family and Flash-Family will be there at the same time. Precautions are set to ensure the four groups don't end up at each other's throats, but with the Bats ability to offend anyone, the Arrows argumentativeness, the Supers vulnerability to being offended and the Flashes big mouths, let's just say they don't come into effect until things are too far gone.
The four families have ticked each other off enough to start fights between all of them, leaving it up to Robin, Red Arrow, Supergirl and Kid Flash to reunite them. The four need to do so before their respective cities get destroyed by the growing tension between the different families, but sometimes a Bat isn't efficient enough, an archer's aim isn't true, a kryptonian's abilities aren't enough and not even a speedster is quick enough to stop fate.
~I do not own any of the characters or locations, only the storyline~