Rushtree becomes the golden mentor.
He was incredibly grief-stricken for a long time when his two mentors died close to one another (official and unofficial), mentors who were like big brothers to him.
But after a long time of working through it and accepting it and feeling happy again, he becomes to apprentices what Martenstep and Cricketfur were to him.
He's patient as a saint. He listens to apprentice's questions without judgement or ridicule and responds to what they need or want. At the end of every training session or lesson, he asks them how they are doing, if there's anything they want to keep working on, if there's anything they want to talk about--related to the lesson or not.
He would be a wonderful mentor regardless of his loss, because that's just the kind cat he is, but he also does it to honour Marten and Cricket and their memory.
Sometimes--whenever he can, really, he tells stories of the brothers. He would talk about all the important stuff they taught him, he would make it clear what amazing Clanmates and friends they were, so much so that on more than one occasion a younger cat would say "I wish I could have met them!"
Too, he talks about all the fun stuff--all the times they played together, all the pranks that were pulled, the jokes that were made--all tales that never failed to make the listeners crack up when he told them.
And every time he talks about them, he can't help but feel their presence with him, warm and loving. And he knows that even if he can't see them, even if they are physically gone, the true part of them, the spirit of them both, are still right there with him.
At least, that's what he believed.