Momozoni and Momoru are twins fyi
Momozoni is a Thaumaturge currently working at the Thaumaturgy Guild in Ul'dah. He's not a very social person and hasn't ever opened up to anyone but his sister. He's very skilled in magic but could probably be knocked out cold by an offhanded slap. He's extremely protective of his sister as she's the only family he has left. Aside from working at the guild or performing alchemy as a side job, he only really reads. The main reason he rarely interacts with people is that he clams up and panics whenever interacting with someone new.
Momoru is a conjurer working in Gridania, although she visits Ul'dah frequently to see her brother. She is far more social than her brother, enjoying conversation and other people's company. Her brother's coddling has led to her being fairly innocent and naive, for her dispositions better or worse. While her brother enshrouds himself in work in a bid to become stronger and make gil, she practitions White Magic as she simply enjoys helping people.
Also Momozoni can turn female if you blast him with enough raw aether.