Recent experimental studies of magnetic field dependent kinetics of singlet fission (SF) processes in some organic semiconductors [i.e. splitting of excited singlet (S-1) state into a triplet exciton pair] have revealed the important specific feature of obtained kinetic curves, associated with decaying intensities I (t) of fluorescence from S-1-state. Kinetic curves, measured in different magnetic fields, are found to cross each other. We show that this kinetic curves crossing (KCC) effect is a general feature of geminate condensed phase reactions, resulting from simple characteristic properties of kinetic schemes of processes. Specific features of the KCC-effect are analyzed in detail with some models of SF-processes.