One possibility is to have nonideal constant phase element CPE in parallel with a capacitance and a resistance. (Z_CPE)^{-1}=C/(jw)^n). Take a look to "Dielectric relaxation in solids" by A.K. Jonscher.
We used that description to fit depressed semicircle in J. Phys. Cond Matter 23 (2011) 496003
First of all non-ideal (Depressed semicircle) or deviation from Debye behavior and origin of different relaxations can be due to Grain orientation, Grain boundary, Sub-grain boundary, Electrode effect and also be due to Interface functional groups. Usually multiple relaxations can be associated with polycrystalline structure too.
You can observe these multiple relaxation from Cole-Cole plot, but some times this plot can't give you sufficient information. Then you can try Modulus plane plot or comparison between imaginary parts of M'' and Z''.