Something I learned recently in my studies: In Korean the term for Nephews/Nieces (조카 Joka) is gender-neutral, so when the dude says, "It's nice to meet you. My nephews!" he isn't leaving out the sister, she's included in '조카.' So it should probably be translated to "My nephews and niece!" since we don't have a single gender-neutral word equivalent in English.
Anyway, thanks for the chapter! :)