From an investigation of varying the steric bulk of a flexible ligand, we have produced a family of structures using similar reaction conditions. Even small changes from a hydrogen atom to a methyl to an ethyl group on the ligand influences the structural outcome, which can also be steered by the nature of the metal source. We employed Schiff base ligands by combining o-vanillin and three different 2-amino-1,3-propandiol units, leading to H3L1 (R = hydrogen), H3L2 (R = methyl), and H3L3 (R = ethyl). The differing nuclearities of the three clusters, 1–3, originate mainly from the steric influence, while this effect is not seen in complexes 4–6, where the general butterfly motif is maintained. We present here the synthesis, crystal structures, and magnetic properties of six new CuII-LnIII complexes, providing valuable insight into future synthetic directions. The topological part includes a table of all CuII–DyIII complexes with nuclearities higher than four and their topological motif. The investigation of the magnetic behaviors reveals that all six complexes show frequency dependent signals in the out-of phase ac susceptibility, which is indicative for single molecule magnets behavior.