Visual Evidence for Raphael
Since February 2007 study of a high-resolution digital photograph of the painting has found that the facial features of the Madonna and Child in the de Brécy Tondo appear to bear a remarkable likeness to those of the Madonna and Child in Raphael's altarpiece the Madonna with the Fish (c.1512/1514, Museo del Prado) and of the Tondo Madonna to Saint Mary (with clasped hands) in his altarpiece Lo Spasimo di Sicilia (1516/1517, Museo del Prado) – both paintings being chronologically close to the Sistine Madonna (c.1513, Gemädegalerie Alte Meister, Dresden) and the likely date of the Tondo [Photographs below].
This suggests the use of the same model(s), perhaps symbolically-idealized.

Detail from
Madonna with the fish

Detail from
Lo Spasimo di Sicilia