My sweet boy is suddenly aggressive?

Hey everyone so I have 3 cats 2 of them are boys Shrimp and Vader. Shrimp is going to be 2 years old next month and Vader is going on 7 months. When I first got Vader at 2 months Shrimp took him under his wing it was so stinking cute. As Vader started to grow they played Alot. Pretty rough on each other but nothing they couldn't handle. Vader Is the type of cat that is overly confident, very low anxiety, and has got to eat outta everyone's food bowl. Shrimp was totally fine with it untill recently (maybe 2-3 weeks ago) he started by hitting Vader when Vader would try to eat his food. Then it just elevated to everytime they play and now it's anytime he sees him. Like no joke Vader can't walk past him or be in the same bed because Shrimp hisses and growls. I'm concerned because poor little Vader used to get so much love from Shrimp and now shrimp seems to hate him. I should mention there's 2 other cats living here besides Shrimp and Vader, Toona who's 6, and our foster cat Lady who is Shrimps age and Shrimp doesn't hiss or hit the girls. Recently like 3 days ago shrimp fell a bit I'll, he's doing much better. I'm going to take Shrimp to the Vet but I have the feeling the Vet isn't going to know anything. It's happened before too. I just want my 2 boys to play and love each other like they used to:-(. Any one had this problem?

Is Vader Neutered? If not, he's at an age where he's starting to mature and going to stop acting like a kitten and start acting like and Adult Male Cat, including becoming territorial and establishing his place in the pecking order. If you haven't doe so, you'll likely want to neuter him sooner rather than later.

If he is neutered, the vet visit is a good idea - any sudden change in behaviour is worth a check . You could also try feeding them separately for a bit to see if that helps.

Also, it could be re-directed aggression from something he sees outside. Since you have a few cats, it may be helpful to have a look at some of our articles on de-stressing for your cats, hopefully you'll find some tips to help get everything back on an even keel.
[article="32390"]Re Directed Aggression In Cats  [/article][article="30316"]Six Surefire Strategies To Reduce Stress In Cats  [/article][article="30274"]Potential Stressors In Cats The Ultimate Checklist  [/article]

Ms. Freya yes my Vader is neutered. I doubt he's trying to be territorial since Shrimp showed dominance since day 1. So idk. I have to find a good vet who specializes in cats. It just caught me by surprise since Shrimp is only aggresive towards Vader. Thank you for those articles I'm going to read them

Just a though, I have been here with my Jasper with 2 cats now (one a male, one a female). Jasper absolutely dotes on a new kitten. He licks them, loves on them, protects them, then they hit around 6 or 7 months and he gets aggressive with them. It seems to be, from what I've read (and I've read myself stupid on things that could be causing Jaspers behaviour) that the kitten reaches sexual maturity and even though they may be desexed, they are suddenly a threat rather than being easy to boss around (even though this may not be the case in the eyes of the younger one).

We've had Jasper checked for health issues numerous times. Cats outside make things worse but aren't the full answer, some of it is territorial but not all of it, it really just seems he doesn't get along with other mature kitties.

We have looked at medicating him (we've done it once before as a last resort but the med. didn't suit him) but at the moment are having success with closing all blinds at night so he can't see out, running feliway diffuser in one room, having lavender plants around the food bowls and he's on a kitty treat supplement containing tryptophan (it's doing the most work).

I'm quick to separate them when there's an issue and we make sure to play with them at least twice a day.

Good luck with them, I hope you can get it sorted. Behavioural issues are so frustrating.

tobilei thanks for your reply. It could be. So I read a post similar to mine on another site and they guy said his cat suddenly became aggressive too. They took hi. To the vet and vet noticed his nails were so long they curled inward. So they trimmed cats nails and he went back to being lovable cat again. So after reading I checked my cats nails for the heck of it and sure enough his side nail was quite long slightly curled in. I trimmed all of his nails and he's doing so much better surprisingly. After trimming his nails it took him a good 4 days to turn down on the aggressiveness. It may have been a combination of what you said and the nails since he was only aggressive to Vader and not to the others.