The age of the pets you Hatch with will not affect the Pedigree of the offspring. The Pedigree depends on the Rarity Points of the Talents and Derby skills that transfer. If more low RP slots happen to transfer from both parents, the Pedigree can be lower than either parent. If more high RP slots happen to transfer from both parents, the Pedigree can be higher than either parent.
KI doesn't promise any pet from Hatching. They certainly didn't promise that stats would always increase in the offspring - especially not with pets that are so close in Pedigree. If you want greater odds for increasing the Pedigree, you need to Hatch with a 2nd pet that is several points higher than the 1st.