KTiOPO4 (KTP) is a well known non-linear optical material. Its crystal structure has highly asymmetric Ti-O bonds, a rigid TiO6-PO4 lattice and K cations trapped in cages. The alkali cations have been the subject of numerous structural investigations. However, these have focused solely on Bragg scattering which gives a time-averaged model of the structure. We propose to study KTP isostructures by collecting total scattering data over a wide range of temperatures. The data will be analysed using the Reverse Monte Carlo method, which will help completing the knowledge about the alkali cation distribution and displacement. It will also provide information on changes in the rigidity of the TiO6-PO4 network, and the Ti-O bond length distribution as a function of temperature. This will enable us to better explain the ferroelectric to paraelectric phase transition in KTP isostructures.