Ferromagnetism is observed below 10 K in [Bi0.75Te0.125Mn0.125]Te. This material has the BiTe structure, which is made from the stacking of two Te-Bi-Te-Bi-Te blocks and one Bi-Bi block per unit cell. Crystal structure analysis shows that Mn is localized in the Bi2 blocks, and is accompanied by an equal amount of TeBi antisite occupancy in the Bi2Te3 blocks. These TeBi antisite defects greatly enhance the Mn solubility. This is demonstrated by comparison of the [Bi1?xMnx]Te and [Bi1?2xTexMnx]Te series; in the former, the solubility is limited to x=0.067, while the latter has xmax=0.125. The magnetism in [Bi1?xMnx]Te changes little with x, while that for [Bi1?2xTexMnx]Te shows a clear variation, leading to ferromagnetism for x>0.067. Magnetic hysteresis and the anomalous Hall effect are observed for the ferromagnetic samples.