Recently, 2D organic–inorganic hybrid lead halide perovskites have attracted intensive attention in solid‐state luminescence fields such as single‐component white‐light emitters, and rational optimization of the photoluminescence (PL) performance through accurate structural‐design strategies is still significant. Herein, by carefully choosing homologous aliphatic amines as templates, isotypical perovskites DMEDAPbCl4 (1, DMEDA=N,N‐dimethylethylenediamine) and DMPDAPbCl4 (2, DMPDA=N,N‐dimethyl‐1,3‐diaminopropane) having tunable and stable broadband bluish white emission properties were rationally designed. The subtle regulation of organic cations leads to a higher degree of distortion of the 2D PbCl42− layers and enhanced photoluminescence quantum efficiencies (<1 % for 1 and 4.9 % for 2). The broadband light emissions could be ascribed to self‐trapped excitons on the basis of structural characterization, time‐resolved PL, temperature‐dependent PL emission, and theoretical calculations. This work gives a new guidance to rationally optimize the PL properties of low‐dimensional halide perovskites and affords a platform to probe the structure–property relationship. Shining white: With the aim of optimizing the broadband white‐light emission performance of low‐dimensional perovskites, isomorphic 2D perovskites DMEDAPbCl4 and DMPDAPbCl4 were structurally designed on the basis of homologous amine templates. The subtle regulation of organic cations leads to increased distortion of the 2D PbCl42− layers and enhancement of the photoluminescence quantum efficiency from <1 to 4.9 %. DMEDA: dimethylethylenediamine, DMPDA: N,N‐dimethyl‐1,3‐diaminopropane.