Thats so sad. I wish I could comfort you somehow, I'm really attached to my pets too. I'm sorry, and I hope their spirits find peace and are able to stay together.
I've had a pet die of an unknown cause, a cat named Squeak. We were staying a hotel or something in Florida, and he just died over night.
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He was perfectly healthy, but he just died. I ahd just gotten used to him too(I was mad at him for replacing our old cats, Precious, Nuit, Fudge, and Babble) My father buried him in an orange grove. And the only other pets(besides fish) I've had die was our collie. She died when I was really young. She had heartworm and had to be put to sleep.
Once again, I am sorry for your loss.
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I don't like losing pets, and I'd just hate it if my cats or dog(who is related to Marble, the dog in the earlier paragraph) died. But, that's how life goes. People and animals are born, live, and then die.