Berry is short for Blueberry. Lavender is his sis not mate they just haven't seen each other in years. Considering Lavender was only a kit when her mother and the rest of her family died. Only Berry was there to look after her. A few years back when Lavender was only 9 moons old, Berry lead a dog off a cliff and went missing. Lavender thought berry was dead, but it turns out he's alive. The song is berry's theme tune cuz it's about him taking that step off the cliff, loosing Lavender and then searching to the ends of earth for her. Listen to it, it kinda fits his story.
