I'm Canadian First Nations and to my people Crows are messengers from the Ancestors and the Grandfathers/mothers. They will also reveal to you the hidden truth in things and lead you back to the light.
The Raven in some of the First Nations Creation stories stories is White returns the light to us by stealing the Sun back so that we can have warmth and survive. In doing so he looses his beautiful voice and his feathers become Black that is what he sacrificed for us. So far from being the messenger of death as in other beliefs to many First Nations Crow's, Raven's and all Corvids have a pretty good role. They can be tricksters as well but in a way that will teach you and make you learn the lesson whilst laughing at yourself.
You can have more than one Guardian / guide / helper. in my beliefs we have nine. Two of these are from your clan / family and the others are personal to each individual and these will be there to help/ protect and guide you when you need them.
As to how you know if they are your Guardians/ guides/ helpers. Well they basically turn up in your life and keep appearing whilst you need them. Using myself as the example here, for me they literally move into my life and live with me in their physical forms.
Through one turning up and needing help due to injury I have ended up rehabbing Corvids (this is the species term for the Raven and Crow family) in particular but all birds and wild life for local vets here where I live.
Every Corvid wild bird or animal with me has all the relevant licenses to be able to stay with me as they are protected by law. Some I can rehab and release again others are licensed into my care for their entire lives as they are unreleasable.
As I write this there are 7 various types of living Corvid's here in my art studio, they each have their own houses for night time. And whilst I'm sitting here writing this I have a Raven perched dozing on my knee and another perched on my foot. So when I say they move into my life and live with me I'm not kidding.
Ok this is a bit more extreme than most people get, but if they are turning up in your life start acknowledging them. Say Hi and chat to them, share some food with them , just make it something healthy like soaked cat or dog kibble ,grapes , walnuts, peanuts, hard boiled eggs with the shells etc. ( Do not feed any bread, pasta as this cause's real health issues with birds and food like avocado, Brazil nuts and garlic n onion , dairy and any processed meats and processed foods are poisonous to them.)
You'll be surprised once they know you and you make that contact, you'll be surprised what they may bring you.
If this link work's here's a photo of the 2 Raven's that I'm lucky enough to share my life with.
https://img00.deviantart.net/7442/i/...ns-dbx9ttq.jpg