It is not unusual for an older cat to dislike a "baby" intruder. They're not happy with older cats usually either. I've had several 6 - 8 week old kittens in my house of 2 older (8 - 12 year old cats - two of them). They don't like the babies at first. The babies learn where to hide (mine like under the refrigerator next to the motor where it's warm). But babies come out and play when I'm home. When the baby is very small I keep them in a bathroom (with bed and litterbox) so they don't get beat up too much.
Latest baby took 4 months to grow up enough to hold his own and to be accepted. The oldest cat still doesn't like him much because youngster is too rambunctious. Second oldest cat is a more tolerant (which is strange because she took every opportunity to beat baby up when he came too close.
It is not unusual for an older cat to dislike a "baby" intruder. They're not happy with older cats usually either. I've had several 6 - 8 week old kittens in my house of 2 older (8 - 12 year old cats - two of them). They don't like the babies at first. The babies learn where to hide (mine like under the refrigerator next to the motor where it's warm). But babies come out and play when I'm home. When the baby is very small I keep them in a bathroom (with bed and litterbox) so they don't get beat up too much.
Latest baby took 4 months to grow up enough to hold his own and to be accepted. The oldest cat still doesn't like him much because youngster is too rambunctious. Second oldest cat is a more tolerant (which is strange because she took every opportunity to beat baby up when he came too close.
It can work, it takes time.