[Luna16]

Well, now that Bramblepaw is her apprentice, maybe over time he starts looking at her as a motherly figure? His own mother was abusive, his father complicit, and now his sister (and the rest of his family but he doesn't care about them) have gone missing. So he's feeling his feelings. They both seem equally closed off emotionally, so maybe that's something she recognizes that in him and eventually they open up to each other a bit more and form that mother/son type bond?

@Frozen Primrose