I am SO PROUD OF THIS Like seriously this character, though I've had him only a year or so less than Kinja, has been impossible for me to draw and I've finally gotten a design that I am proud of.
In the current timeline he would be 25(Kinja being 24).
I haven't drawn Sirk(let alone drawn him well) since 2009 and I think I finally nailed it! He was my main villain of the sonic au I created, from the planet of Mythiria(which had their own version of the Chaos Emeralds, the Mythirian Jewels, but each controlled a specific element and the rainbow mythirian jewel was the most powerful of them all and usually inherited by the royal heir unless someone is born with the jewel as a birthmark). He is the prince of Mythiria and the jewel was his birthright, but his sister, Princess Semir(known as Remi once she moved to Mobius) was born with the birthmark, being the first royal to have both the nobility and birthmark. The jewel was given to her upon birth, but when she was about ten and training she couldn't control her powers and killed quite a few of their guards and the king and queen. He was 17 when this happened.
Terrified, Sirk rallied against her and tried to kill her, yet was only able to chop off one of her tails. He now proudly wears it as a trophy. He successfully drove her off of the planet, but with her went the Rainbow Mythirian Jewel(or so he thought, turns out Semir's best friend was given it to safeguard it). He continued to hunt it down and take it for himself to protect his people as King.
After one year of searching Mobius to hunt down the jewel, he met and fell in love with Kinja. Her brother, Kinjuaou, was very wary of him and refused to let Kinja see him especially after Sirk proposed and asked Kinja to come back to Mythiria to rule as queen. Led to a huge battle that took Kinjuaou's life. Kinja, unknowingly pregnant with Sirk's child, saw the battle and grew an unfathomable hatred towards him, fled to knothole and was protected by the freedom fighters until she gave birth and underwent a identity change as Senna Stone, a rock singer who ended up forming Clockwork Penguin. After becoming Senna, she returned back to her old home and lived peacefully.
I haven't figured out this part of the story yet but Kinja and Sirk's child(I forget her name but probs will rename her anyway) was somehow found again by Sirk, and he took her back to Mythiria to raise her. In his absence his close friend Xial, with the help of the late king and queen's advisers, ruled Mythiria and very happily returned the throne upon Sirk's return.
To this day, the Rainbow Mythirian Jewel is still 'missing'.