Did anything else change 2 years ago? Did you increase the number of cats,
or decrease or change their available space?

Margaret S.

I would keep them separated except under supervision and I would definitely
add a couple of Feliway diffusers in the house.

Try putting Spooky on a halter. It may or may not work, but I have a
similar problem with Chase and Kira. Chase likes to chase (at least we
got his name right). When I put the halter on him, he slinks around.
He can physically do anything, but he seems to think that he can't.
So, he won't chase her when he is wearing it. We call it is twisted
halter. It looks kind of like a halo, twisted into halter shape. Put
it on him and he becomes "angel boy".

Whenever he acts up, we put the halter on him. After a couple hours,
we take it off, and he is usually better behaved. It also acts as a
good deterrant. He knows what it is, and he seems to understand why he
wears it. When he is mildly acting up, I show it to him, and he
usually behaves better.

If that doesn't help, you may need to keep him on a leash part of the
time.

Also, does Simba run? If Simba runs on sight of Spooky, then you have
a cycle that needs to be broken. Simba runs because Spooky chases. But
Spooky chases because Simba runs. At this point, it doesn't matter how
it started. They both have to relearn the correct behavior. Spooky has
to learn not to attack. And Simba has to learn to hold his ground. I
had a situation like this many years ago. It took several months, but
we were able to eliminate the chase/attack behavior, and they were
able to hang out in the same room without any problems.