Was Eggs originally going to be the character you made him into? I imagine him with a fez, by the way.
Zennish was originally a urchin-ish character that Pate and Vessal stumbled upon in an alley and started taking care of without adopting.
Eventually it became mostly Vessal doing that because he knew what Zen was going through more intimately, and helping Zennish overcome his situation would have forced Vessal to reexamine how he saw himself.
And the similarities between Zennish’s attitude and his own would lead Vessal to think Zennish would be the best replacement for him [Vessal], if/when Pate needed it.
None of that fit into the plot, so Zen caught a break and got hired as a page instead, meaning he got servants rations- but he still had a lot of weight to put on, hence him scrounging around for extra food wherever he could, without actually stealing and risking his job. And Vessal’s tendency to forgo food so he could get back to work made him a more suited than the other pages at being meal-mate to Zen, who was never very social. (Another thing he and his mentor have in common.)
Basically Zennish’s circumstances changed radically, as did his relationship with Vessal, but his character remained much the same. He’s still what Vessal would have been like if he had gotten out of his neighborhood a few years earlier.