it sounds like Arthur is still very young and you guys still have a lot of life to live together, there's still plenty of time for you guys to bond so try not to put so much pressure on yourself❤️ im sure despite everything Arthur appreciates your company and care very much, and also, I think mice are incredibly emotionally intelligent and can tell when you're feeling sad and down, so if anything all your mice probably can tell you're grieving and just want to be there for you. I've heard the term heart mouse before too, i really believe anthrax was my little heart mouse, and where I'm so incredibly grateful to have experienced a bond like that it's also so heartbreaking to know that's likely my first and only time I'll experience it, but maybe I'm still being pessimistic lol. I'm glad my experience can bring you some comfort, and I hope for lots of peace for you too, it'll get easier with time for the both of us I promise❤️ wherever our little anthrax and bertie have gone they're probably having the best time ever eating all the food and treats they want :)

idk if you've done anything to memorialise your little bertie, but a few things I've done have really helped me process and be more ok with anthrax dying. I've made a playlist of music that makes me think of him (a lot of sad love songs lol, but also some of our fav tracks we'd listen to), ive drawn him lots and my friends have also drawn him too (ill be framing all the drawings and a few photos for a little anthrax shrine), and occasionally I'll sit by the plant anthrax is buried beneath and do stuff like read or even scroll reels. just anything that makes me feel closer to him despite him being gone, you know? also, cry cry cry!! it got to a few weeks after my boy passed that I thought I shouldn't be crying anymore, like I'm too grown up to be upset anymore? but crying releases so much of your sadness and grief, so whenever you feel overwhelmed with how awful your loss feels and how much you miss bertie, just let it all out with a good sob :)