We used a set of approximately 200 Arabidopsis thaliana (L.) Heynh. genes that are involved in the control of flowering time as a reference to identify orthologous (or homologous) counterparts of these genes in three legume species, that is, Lotus corniculatus L. var. (FPIs), and floral meristem identity. Many key genes, including the FPI genes FT, SOC1, and LFY, are conserved in the legumes while CO, FRI, FLC, and FD were not. Eighteen genes were conserved as single copy genes in all three legume species, including GI, VRN2, COP1, and TSF. The chromosomal distribution of paralog-rich genes revealed differences in the major evolutionary processes affecting flowering genes in legumes, including whole genome duplication in soybean, tandem duplication in M. truncatula, and ectopic duplication in L. corniculatus var. japonicus. High divergence was observed among the members of large gene families, most containing transcription factors, indicating the accumulation of gene copies and gene divergence during evolutionary adaptations to environmental changes.