How very sad for little Shadow but most of all for you Aly.
Shadow is happy and having a wonderful time with all the RB kitties. You are left behind to grieve. You can't feel guilty because if you were doing something wrong then the other kittens wouldn't be ok. I felt the same way when I lost two kittens but I know that I gave all that I knew how to give. The pain will get better with time and you will find peace in knowing that he had a wonderful life with you. So many babies die without love and care. Shadow had a great life full of love. I don't think any of us can ask for more in whatever time we spend here on earth.
Thank you for caring for a precious baby for his short visit here.

{{{HUGS}}} Good thoughts and prayers from me and my nine.