premise: Gaddo Gaddi (c. 1239, Florence – c. 1312, Florence) was an Italian painter and mosaicist of Florence in a gothic art style. Almost no works survive. He was the father of Taddeo Gaddi. He completed mosaics on facade of Santa Maria Maggiore in Rome. The "Coronation of the Virgin" mosaic over the inside door of Florence Cathedral, dated 1307, is also attributed to Gaddo Gaddi.
hypothesis: Taddeo and Gaddo Gaddi are siblings.
reason: Gaddo was the father of Taddeo Gaddi, so they cannot be siblings; the algorithm may not know what siblings are or may not know they are exclusive terms.