Portal 2 on Steam adds split-screen to co-op mode, Big Picture support - Polygon
Portal 2 Pc | Peatix
Portal 2 Patch Tweaks Co-op, Adds Split-Screen Via Remote Play
Latest Portal 2 Update Adds Local Co-op, Controller/ Android & iOS Remote Play Together & More : r/pcgaming
Portal 2 PC adds splitscreen co-op - GameSpot
Portal Knights - Vertical split screen is being added to Portal Knights as part of Update v 1.1, coming soon to both PC and console! We know this is a popular request,
Portal 2: Pretty Much Every PS3 Question Answered (And That Cake Thing, Too) – PlayStation.Blog