...Tanidio thinks about how Bun cares about the babies. Chrisor cares about the babies because more children going to Hell will make Hell more powerful, and that hastens Hell's inevitable victory and pleases Asmodeus, and both of these facts mean that Chrisor will spend his afterlife with more and better slaves to shape as he likes. Tanidio... mostly cares about his mother not having to go hungry anymore, and the people paying him would care about the babies, so he cares about the babies.
Bun... just cares about the babies. Not just because they're paying him. It seems like Bun would pay them, if it meant that fewer babies would make the Boneyard.
Tanidio didn't really realize you could care about people you haven't even met. Or-- he knew that Sarenrae thought that every single soul no matter how obviously Hell's should be hers, which is why she petitions for them. And he knew that Iomedae wants the whole world to resound to the greater glory of Iomedae. And he knows that someday every corner of the universe will be Hell. And if you're far in the service of Iomedae or Sarenrae or Asmodeus, then you start thinking about people you don't know like they're a little bit yours too.
(Tanidio, who is not that far in Asmodeus's service, knows that his mom is his, and he guesses her slave as well because of the definition of ownership, and has never really felt much desire to own or care about anyone else.)
But Bun... doesn't seem to think the babies are his...? It is a strange, confusing thought and Tanidio isn't really wrapping his brain around it. He doesn't want to save the babies so that people will be grateful to him, or the Buddha, or anything like that. Bun is a very strange person.
There is something warm in Tanidio's chest, which is probably the wine.