I've seen a lot of people referring to Kindred as a "she". Kindred are a "they", They're both spirits, Lamb and Wolf.
A lot of people seem to think Kindred is Lamb, and Wolf is only some kind of pet. I understand that since you directly control only Lamb's body, it can be pertty confusing but still, Kindred is a whole composed of two spirits and when you are referring to Kindred, you must use "they". If you use "she", you are then talking about Lamb, but then you are not talking about the champion but only half of it (them?).
Hope that's clear, now.
Edit: Riot says "they", so this is clear what should be used.
Edit 2: The man they're talking about in _Listen to their tale_ is a metaphor for death, not an actual man, so "he" isn't valid.