Important information;
Spirit Animals and their heritage?
Spirit animals in fact do not come from parents or have a lineage. They come from what is called "The Veil" which is where the energy and magic for spirit animals is basically kept. They're more or less reincarnated from previous versions, bonds, etc. but will have no memory whatsoever of these memories.
How do you know if there is a bond?
Spirit animals when bonded with a human will either have a relic that they appear from on their bonded person or they will have a tattoo from the spirit animal.
is this marking specific?
Each relic/tattoo is up to the player playing their character! If they want it to represent their bonded animal, if it's just a fancy looking mark, etc. that's up to them!
Where will spirit animal bonds be made?
Each bond is specific to the animal. It's usually made at random with the animal appearing to the human. They can converse with each other just as normal people talk. Other bonded animals can speak to bonded humans and vice-versa. But if someone doesn't have a bond, they can't speak to the animal.