Does the kind of animal your familiar is a permanent thing? Like would Roman always would have a cat as a familiar even if his life was completely different? Even if he had never met Dizzy that day?
here and here there’s some meta explaining this but, short version - not necessarily
the animals are a reflection of the witch/the witches personality
(Greta and Roman both have predators, for example, Greta a coydog, a pack hunter, which has symbolism tied up in her relationships with both Virgil and Durant, and Roman has an ambush predator. Roman, as a fairy hunter, hunts alone but like a domestic cat is not actually meant to be a solitary creature, instead part of a colony)
if Dizzy or Jax died before Roman or May (which they can, i talked about that in the above asks too - theyll live as long as the witch on their own but can be killed just like any other animal) they would get a second familiar, but that familiar would be a reflection of who they were at that moment.
May would almost certainly get another bird, but would she get another buzzard? unclear. She’s a much different person than she was when she was ten and full of too much bitterness for such a little girl.
Roman has had far less time with Dizzy but a lot more happened in that not-quite-10 years than most 18-year-olds have to deal with, so im even less sure on him