Gotham Knights will not support four-player co-op

The Bat Family only works in pairs, apparently.

Gotham Knights will have four player co-op for all Batman's sidekicks

Gotham Knights Is Set To Get A Free Four-Player Co-Op Mode In November

Watch 13 minutes of Nightwing and Red Hood beating up thugs in Gotham Knights

Gotham Knights - FAQ

Gotham Knights Update Adds New 15 Floor Raid, Stronger Gear, and Accessibility Options

Looks like there will be 4 player coop after all. I was hoping for news on performance mode on consoles but oh well. : r/GothamKnights

It's Official: No 4 Player Co-op Multiplayer For Gotham Knights - Gameranx

Gotham Knights: Four game experiences in one – PlayStation.Blog

Gotham Knights Dashes Fans' Hopes, Will Only Have 2-Player Co-Op

Gotham Knights will let your progression in a friend's world affect your own - Dexerto

Gotham Knights' Four-Player Co-Op Mode Heroic Assault Launching November 29

New Batman Gotham Knights game: Everything you need to know