Three series of aliphatic random copolycarbonates, poly(heptane-co-dodecane carbonate) P7C-P12C, poly(butane-co-dodecane carbonate) P4C-P12C, and poly(butane-co-heptane carbonate) P4C-P7C, were synthesized by a two-step polycondensation process. The organocatalyst 4-(dimethylamino)-pyridine was used for the first time to prepare copolycarbonates, as an alternative to metal catalysts, to avoid the toxicity of the remaining catalyst impurities that are difficult to remove after synthesis. Differential scanning calorimetry (DSC) studies demonstrated the isodimorphic character of the copolycarbonates showing pseudoeutectic points and crystallization in a wide composition range. Wide-angle X-ray scattering (WAXS) results displayed changes in crystallographic plane spacings possibly because of the isodimorphic behavior of the systems. Two double crystalline copolymers were obtained, that is, 85/15 P4C-P12C and 80/20 P7C-P12C, as they correspond to pseudo-eutectic compositions. Remarkably, for the 80/20 P7C-P12C copolycarbonate, we found a novel behavior. This copolymer exhibits both coincident crystallization and coincident melting during nonisothermal DSC runs. However, WAXS revealed that the material is double crystalline as it contains crystals from P7C-rich and P12C-rich phases. This is the first example of a double crystalline polymeric material that exhibits a single crystallization and a single melting peak in spite of being double crystalline. Comparing the results obtained for the three series of copolycarbonates, we conclude that it is easier to incorporate a shorter repeating unit chain segment in a crystal formed by a larger repeating unit chain segment.