We present the results of the temperature dependences of ac and dc susceptibilities, high-field magnetization, magnetic relaxation, specific heat, and electrical resistivity of Pr2CuSi3 and Nd 2CuSi3, compounds previously shown in the literature to exhibit interesting properties. Itis observed that the investigated compounds undergo a ferromagnetic phase transition at a characteristic temperature T C (=9.8K for Pr2CuSi3 and 5.6K for Nd 2CuSi3), where zero-field-cooled dc susceptibility shows a rapid increase followed by a sharp peak just below TC. Below T C, the magnetization curve displays an open hysteresis loop and a steep rise at low fields, while irreversible magnetism and long-time magnetic relaxation effects can be observed. Furthermore, near TC both the real and imaginary components of the ac susceptibility show a large peak with a small frequency shift of the peak position, and a sharp anomaly appears in the specific heat and electrical resistivity curves. These unusual features observed for Pr2CuSi3 and Nd2CuSi3 strongly suggest the formation of huge ferromagnetic clusters accompanied by a very weak spin-glass-like effect in both samples. The obtained results are discussed by comparing them with the data reported for other 2:1:3 intermetallic compounds and some alloyed compounds with different stoichiometry.