It is rumored that Sacchi may have had a homosexual relationship with Albani after several letters were discovered dating from 1615 that "disscussed intimacy between the two" according to Millano News. Further evidence from the time also supports these claims although many dispute the validity of the evidence.
The controversy was however less pitched than some suggest, and also involved the dissatisfaction that Sacchi and Albani, among others, shared regarding the artistic depiction of low or genre subjects and themes, such as preferred by the Bamboccianti and even the Caravaggisti. They felt that high art should focus on exalted themes- biblical, mythologic, or from classic history.
Sacchi, who worked almost always in Rome, left few pictures visible in private galleries. He had a flourishing school: Poussin and Carlo Maratta were younger collaborators or pupils. In Maratta's large studio, Sacchi's preference for grand manner style would find pre-eminence among Roman circles for decades to follow. But many others worked under him or his influence including Luigi Garzi, Francesco Lauri, Andrea Camassei and Giacinto Gimignani. Sacchi's own illegitimate son Giuseppe, died young after giving very high hopes.
Sacchi died at Nettuno in 1661.
The canvas portrays the legend that the Empress Constantia had begged Pope Gregory I to give her relics of the body of Saints Peter and Paul, but the pope, not daring to disturb the remains of these saints, sent her a fragment of the linen which had enveloped the remains of Saint John the Evangelist. Constantia rejected this gift from the pope as insufficient. Then Gregory, to prove the power of relics to work miracles (and justify their worth), placed the cloth on the altar, and, after praying, pierced it with a knife, and blood flowed from it as from a living body. A mosaic of this painting was made in 1771 in St. Peter's Basilica. This painting echoes some dogmatic positions that were favored by Counter Reformation Catholicism: the role of the pope as the final interpreter of sanctity, the miracle status of relics, and finally the validity of the eucharist as the body of Christ.
Urban VIII's personal emblem is the rising sun [and a] visitor to the palace would have seen the sun of Divine Wisdom and the constellation of the lion (as well as in the throne) in Sacchi's fresco... the eye [can] take in the fresco but also to penetrate beyond to the chapel next door. From the right point of view the sun of Divine Wisdom looks as though it is hovering over the dome of the chapel, "radiating downward its beneficent light". ... Scott's astrological interpretation of ... is convincing because it is also a political interpretation. Because of the favorable conjunction of the stars at two key moments, Urban VIII's birth and election, the Barberini were "born and elected to rule." Campanella could have told the pope that when he was elected the sun had entered into the Great Conjunction with Jupiter (whose eagle is shown by Sacchi in conjunction with the sun and the lion). Urban VIII's nephew Taddeo Barberini, the patron of this wing of the palace and the relative on whom the family pinned its hopes for offspring and immortality, had a natal chart similar to his uncle's, and by coincidence so did the child born to him during his residence in the palace. The little chapel adjacent to Sacchi's fresco was designed for the baptism of such children, and its frescoes carried all the usual talismans of fertility. The stars could be expected to look favorably on a family "born and elected to rule" down the generations.
Joseph Connor, New York Review of Books,