Pets are important to families too, and this condolence letter can help share the sorrow of a grieving cat owner.
Dear {Recipient},
I am writing today to express my great sorrow that your cat, {Cat}, passed away. {Cat} was a very special animal, and I know you had {him/her} for a long time. I remember that story you told me about how {happy cat story}. You took such good care of {him/her}, and I know {Cat} had a very happy life.
In some ways, losing a pet can be unexpectedly difficult, and I know not everyone understands this kind of grief. So, if you would like to talk about it, please contact me at {phone/email}. I do understand, and I'll always be around to listen and help if I can.
Your friend,
{Sender}