We only followed Altair for a relatively short while, so we never saw him past his prime. On the other hand, Ezio's gotten 3 games for the entire range between 17 and mid-50s (No dates for Revelations yet). So yeah, he's the old man of the series.
No it isn't. If you'd bothered checking, doubleleaf is called genmaipudding here. I'm not sure why, but he is. It's not uncommon for artists to have various names.