An enhancement in near-scission α-particle multiplicity was observed in the ¹²C + ²³²Th fission reaction at a beam energy of 69 MeV in a recent experiment [Y. K. Gupta et al., Phys. Rev. C 86, 014615 (2012)]. The excess α-particle emission was attributed to α-transfer induced fission, where α-particle transfer followed by breakup of ⁸Be into two α particles in coincidence with fission fragments (FFs) was observed. In order to further verify this transfer-breakup source, α-particle energy spectra have been measured in coincidence with FFs in ^12,13C + ²³²Th reactions at various relative angles with respect to the beam and FF directions at a beam energy of 74.5 MeV. The α-particle multiplicity spectra were fitted using a moving source disentangling analysis. The features of multiplicity spectra clearly demonstrate the presence of transfer-breakup events in ¹²C + ²³²Th fission. The contribution of α-particle multiplicity from transfer-breakup events in the ¹³C + ²³²Th reaction is seen to be negligibly smaller than that of the ¹²C + ²³²Th reaction. After taking into account the transfer-breakup source, the pre- and near-scission α-particle multiplicities follow the recently developed heavy-ion systematics for both reactions. These results conclusively affirm that transfer-breakup is a potential source of α-particle emission in fission reactions, induced by α-cluster projectiles such as ¹²C.