"Your sister?"

Maybe he should know better. With the way the man's voice trails off, it's easy to assume he might not want to talk about it. And in some cases Inigo may have realised that and been sensitive enough to back off, but this just happens to be a topic he is very specifically interested in.

".. You have a sister? What is she like?" At least he's asking that rather than how she's in danger - maybe there's some part of Inigo's brain still trying to not be too rude.