Friendly Nieghbourhood cats hate my new cat?

my new cat has been mixing with the other 4 nieghbourhood cats recently i'm worried because all four of theres cats live in the same home all introduced in different years the first 14 years ago the 2nd 11 years ago the third 2 years ago and the 4th one year ago and mine 2 weeks ago all 4 get on great and always have no fighting but when my new cat came down the stairs to see them gently meowing in what seemed a friendly way sniffing thier noses each at different times 2 of them where hissing vigoursly at him the youngest one hissed at him them stressed from seeing him ran over and clawed me, which confused me because he seemed so nice in the past and the 4th cat who seemed so friendly had the worst wrath and had a huge go at him hissing and meowing when i heard her i assumed they we're having a fight, to find my own cat huddled up in the corner afraid of her, worried i grabbed him and pulled him inside, i don't know why they hate him because all of these cats when they first met immediantly got along, do you have any idea whats happening thankyou.