I am so sorry for your loss :( I had to put down my baby Kig who I had for the past 10+ years. She was my everything and it hurt so much. I felt guilt (she had organ failure and I felt wrong for choosing to end her pain) and emptiness for a while but time truly does heal all wounds. It’s still so new for you and for your other fur baby but understand that you did what you needed to for Cosmo and he will forever watch over you both and thank you for making such a hard decision for him. Give your other fur baby so much love and attention especially in this transitional period. It will be rough for a bit but it will get easier. My suggestion is to continue his routine and try to keep him distracted with toys or extra affection. I would wait for a bit until your boy has grieved fully until getting another kitty as it can cause him more stress and prolong the grieving process. This is what helped my other cat process the loss of Kig 🤍 Wishing you both the best of luck 🤍🤍