my 8year old mail cat billy martin has been getting sick {vomiting} after eating ? he also eats all of his sisters [willow] wet can cat food ? any help would be wellcome ?

There are multiple things that could be causing this, some minor some major. You definitely need to bring your car into your vet to be seen.

I would definitely take your male cat to his vet to get checked out

what does the Vet say of your cat .You need to take care of your cat.

I agree with all of above comments...get it to a vet asap

Have to see vet call humane society