A mutual situation is a situation with two participants A and B in which the relation between A and B is the same as the relation between B and A.
"A mutual situation can be defined as a situation with two or more participants (A, B, . . . ) in which for at least two of the participants A and B, the relation between A and B is the same as the relation between B and A." (Haspelmath 2007: 2088)