Who? Cal Kestis is from the video game Star Wars Jedi: Fallen Order, and the sequel, Star Wars Jedi: Survivor. I have also read Star Wars Jedi: Battle Scars. Let me know if you want me to avoid plot spoilers for the games or the novel. I am up to date with Jedi: Survivor.
Timeline: His canon point at the beginning of Fallen Order is five years after the Prequels era when Empire has appeared, fifteen years before the Original Trilogy era when the first Death Star is destroyed. The Jedi: Survivor canon point is five years after the end of Fallen Order. Happy to play him from any canon point, including far in the future, and far in the past for baby Cal on Bracca or even in the Jedi Temple. I only have icons for Fallen Order era Cal at present.
Backtagging: Yes absolutely. If you aren't sure if it's been too long, message me, but it probably hasn't been!
AUs: I adore them. What if Cal had had a different master? What if Order 66 never happened? What if a wormhole opened up and he dropped into a different universe?
Threadhopping: Ask first.
Fourthwalling: I don't mind making a few jokes about Star Wars being fictional in your character's universe, but that can't be the only thing the thread is about.
Crosscanon: YES PLEASE.
Timezone: Central Standard Time (UTC -5)
Contact: PM this journal

Hugging this character: Sure, Cal is up for hugs.
Kissing this character: His experience with things like that is minimal, if it comes out of the blue he'll shut down a little and might not open back up.
Flirting with this character: FLUSTER him. He might even flirt back.
Fighting with this character: Yes, but he is a Jedi, so he is very good at it.
Injuring this character: WHUMP him.
Killing this character: Let's talk about it first.
Using telepathy/mind reading abilities on this character: He's a Jedi, he will probably know something is happening, but talk to me and we can figure out if your character would make it through his mental shields, and what's back there if they do.

M/F or M/M: Yes. I am a multishipper and very easy to convince. If our characters have chemistry, I will probably ship them. That said, I adore found family just as much, especially for characters like Cal who never really had family growing up.
Canon: I tend to see Merrin as his sibling rather than romantically, but I'm not completely opposed to the ship. I am very into Cal/Trilla as a ship.

Canon:

Cal has a power called psychometry, which allows him to sense memory echoes in objects he touches. It's a rare trait and he was born with it, it can't be taught, only refined.

He carries a double-bladed lightsaber that can split into separate blades. It is the only thing left from his master, Jaro Tapal, who died getting Cal to safety during Order 66.

Cal landed on the planet Bracca when he was twelve, a scrapyard planet, and spent the next five years hiding his Jedi powers and working at the very dangerous job of breaking ships. It gave him an uncanny ability to climb up, over, or through almost anything.

BD-1 is Cal's explorer droid, always found hanging from a harness on Cal's back. BD is a talkative droid, though he only speaks binary, but Cal will frequently talk back to him, as BD was Cal's only companion while exploring different planets. BD can slice security droids, probe droids, terminals, and takes scans of any interesting flora, fauna, or dead bodies he comes across. BD-1 is the best. That's canon.

Cal is the same age as the clone troopers, including Boba Fett, and Han Solo. (Fun fact, Boba Fett and Han Solo are the same age.)

Headcanon:

Cal Kestis and Caleb Dume AKA Kanan Jarrus were best friends at the Jedi Temple. I would LOVE to do something with this.

Cal became Jaro Tapal's Padawan when he turned ten years old.

Jaro Tapal led the 13th Battalion on the Albedo Brave, but he insisted on assignments that kept them away from active battle because of the age of his Padawan. He did not allow the clone troopers to call Cal "commander" like most Padawans, and preferred they call him "Jaro" rather than "General Tapal." As a result, the atmosphere on the ship was lighter and more focused on friendly but intense competitions between trooper squads to keep them sharp in lieu of front line battle. Cal picked up this appetite for friendly competition, but despite this he does not have a sabacc face and is terrible at gambling.

Quinlan Vos trained a youngling Cal in using his psychometry. It is a very rare ability and no other active Jedi had the skill at the time it emerged in Cal. Quinlan was not in a position to take Cal on as a Padawan, and Cal always felt a little disappointed by that, which manifested later as guilt when Jaro Tapal died for him.

Prauf found Cal and took pity on the little human right away, and gave him as much advice as he could when Cal was growing up on Bracca. This included "always know how to put together anything you take apart," so Cal is very good at repairing ships and droids.

Fun Conspiracy Theory That I Don't Take Seriously:

Cal Kestis is Obi-Wan Kenobi's son and neither of them know it.