In order to prove his theory about sounds correct, Champollion needed to identify a second name that contained some of the same hieroglyphs as Ptolemy's. There weren't any on the Rosetta Stone, so Champollion turned to copies of hieroglyphic inscriptions from other Egyptian monuments and temples. But no matter how many copies he examined, he couldn't locate a name that met his requirements. —The Riddle of the Rosetta Stone,
James Cross Giblin

How were Champollion and Young similar?

Both thought hieroglyphs represented sounds and tried to prove it by translating names.
Both believed hieroglyphs represented sounds and looked for proof in Egypt.
Both thought hieroglyphs represented sounds and tried to prove it by studying Greek monuments.
Both believed that hieroglyphs represented sounds and tried to prove it by looking for a second Rosetta Stone.