Name: Treestep (Becomes Treestar when he created one of the four clans in my story TreeClan)

I really like this name. Both the prefix (Tree-) and suffix (-step) is underused, so it's pretty origanal. I have sevral OCs with the suffix -step. Littlestep, Fawnstep, Lightstep, and Flashstep.  I still like it though!

Age: 25 moons

Young. 

Appearance: smallish brown thick set tabby tom with white paws

Maybe change the white paws to ginger. A lot of cats have white paws, may of my OCs do. 

Personality: Friendly and quite honest. However has the tendency to panic, become stressed and worried easily when under pressure

Add some more flaws, and some unflaws too. He seems kind of one-deminsinal. 

Clan: OakClan (Once OakClan splits up after Hellstar's reign, he creates TreeClan)

I like the prefix Oak- with  anything. 

Backstory: Treestep was born and raised in the ancient OakClan (OakClan roamed around 200 years that's a long time ago, before the creation of TreeClan, HawkClan, RainClan and DawnClan. Those four clans descended from OakClan). After Rosestar was killed, an ambitious cat named Hellfire (Yes, I know cats won't know what 'Hell' is. I'm planning to either change it or he changes his name. This whole AU is a work in progress) took her place instead of the deputy (There is a reason why, but it will be too long to write) Treestep had to stay loyal to the new leader who changed the clan's way completely.How much?  Five cats began a rebellion, but three were executed why only three? why werent' Hawkfire and Raintail killed too? and the other two (Hawkfire and Raintail) were exiled (They then found a new territory and created HawkClan and RainClan). After Hellstar died, the clan split into two and travelled away to a new territory. Dawnstorm created DawnClan and Treestep created TreeClan. They moved into the territory with the other clans.

This is good. Just change Hellstar. 

Kits: Yes (Later on in his life when he is leading TreeClan) Sandkit and Mudkit

Aww! Name them Sandstripe and Mudwing!

Crush: Yes (He had always had a crush on his friend who he had grew up in the nursery with named Riverwhisker, but she went with DawnClan) Later on in his life he falls in love with Skystorm.

I have an OC named Skystorm! And Riverwhisker sounds like a tom, but...

Mate: Skystorm (When he is leader of TreeClan

No comment. 

Others: Treestep had an apprentice named Daisypaw who bravely gave Hellstar death berries to remove a life and was killed as punishment for what she did.

That's cool!

This is a well thought out OC, but maybe change alittle bit. I give Treestep an 8/10.