Has he ever shown any aggression towards a person, or does he just hide?
Lynn
Hi,
Just because he's attacking the other cat doesn't mean that he will start going after people as well. As long as your granddaughter doesn't corner him somewhere where he can't get away from her there's any reason to think he would bite her. (He may not even try to bite her if that does happen.) Attacking other cats and attacking people are usually not related issues. However if you are still really concerned about it shut Simon in a room when your granddaughter comes to visit so she can't go near him. Here is a link to a page about aggression in cats;
http://www.sniksnak.com/cathealth/aggression.html
You might want to take him in for an exam and blood work sometime though. Sudden behavior changes (especially aggression) can be due to an underlying medical problem.
If you have further questions let me know. If this answers your question please click accept. Thank you and best wishes.
Veterinary Assistant
worked at a vet clinic for 15 yrs, BA in biology, have had cats most of my life