Welcome to the Cat Site! It's a great place to ask all kinds of questions - -so many members have experience in SO many things that you can usually find someone who can answer a question. So glad you found us here!
That said - - you actually asked something I'm not sure of! I think it might be - - but I always have trouble feeling sure on Fever Coats (I've only seen a few in all my years of work at cat shelters!). What a gorgeous little thing! I'm so sorry to hear about the little one's mom. Are you taking this sweetie into your home to keep? She's obviously very comfortable with you! I'm so glad you saved her - - she's too young to be outside alone. And it goes without saying that being out wherever she was with mom is too dangerous for a little one.
Keep us posted on what you decide to do with her (I vote "keep" ---- she's too cute to let her go!). If you have any questions about bringing her in safely, let us know!
Yes, that looks like fever coat to me. My guess is that he will turn out to be a black cat when he matures. It is sad that his mama was killed, but it's good that he has you to take care of him now!!