They agreed to stay connected for hours in their provisional support group, looking for answers in their counterparts.
I want to change the bold part to say that they all shared the same problem.
Might end up using one of the above, but I feel like I need some more options to weigh in.
Edit for context: they all share the same rare cognitive impairment
Best Answer
There's the straightforward co-sufferer: "one who suffers with another." (Free Dictionary)