I started Princess Agents today. It isn't my first C-Drama but can someone explain the whole '5th sister, 6th sister, 7th sister' thing. A friend of mine also started Princess Agents but it's her first C-Drama and it raised some interest in me. I simply told her it had something to do with ranking.

Mm, I didn't watch this drama, but it's just the order of birth so 5th sister would be the fifth oldest of the daughters, 6th sister would the the sixth oldest of the daughters, and so forth.