My cat, Trevor, was 3 years old when I brought home Andy who was about 8 weeks old at the time. Trevor did some hissing which usually made Andy run and hide under something. We kept them separated during the day when no one was home and in the evenings they were put together with close supervision. After a while when Trevor realized Andy was pretty harmless things improved. Today they are best buddies. I would just recommend you take it slow and easy with your two and only let them interact for now anyway when there are people to observe. Trevor never hissed outside the door where Andy was but he certainly "parked" there a lot in the beginning and tried to smell him under the door. Good luck and keep us posted!