同病相怜tóng bìng xiāng lián
[fellow sufferers have mutual sympathy;those who have the same illness sympathize with each other;adversity makes strange bedfellows;company in distress makes trouble less;fellow sufferers commiserate with each other] 比喻因遭遇同样的不幸而共相怜恤
同病相怜,同忧相救。——《吴越春秋》