Nayden Marcellus Genkov isn't always a werewolf. Wizardingly speaking, he was perfectly normal, being the only child of Stanislav Genkov, a Bulgarian wizard with Hungarian descent, and Bianca (née Jackson) Genkov, an American witch.
Nayden was born and raised up in a small town in Maine, the U.S., where both magical and muggle residents could be found. With both parents working at the American Ministry, he was looked after by his nanny. Certainly, he didn't receive much care from his workaholic parents. Though, his childhood wasn't too miserable, as he could always play with other children in the neighborhood and from the muggle elementary school in town which he attended to. Occasionally, he would create some troubles, just like any kids would do - not just because he quite enjoyed doing so, but also to attract attention from his parents.
However, things changed when he was 10. One night - a full-moon night - when Nayden wandered off to the forest, he encountered a werewolf. At that time, he didn't clearly know what he was facing, but his instincts told him to scream and run. So, he did, only that he was, of course, too slow. By the time his parents got to him who was unconsciously laying on the ground and severely injured, he was already bitten, and the werewolf was nowhere to be found. Surely, Nayden wasn't killed. Yet, when a full-moon was observed a month after the incident, both his parents and he were certain that he was turned into a werewolf.
Despite being afflicted with lycanthropy, he was accepted to American Academy of Magic at the age of 11. With help from the professors, he was able to hide the truth of being a werewolf from other students, being brought to a forest for transformation every month at the full moon. Unfortunately, three months before the end of term, his secret was eventually discovered by some students. The news spread out and he was treated as a freak - a monster - by other students and the parents of the students. No longer able to endure it, his parents arranged a transfer for him in his second year to a wizarding school in Eastern European - the Slavic School of Magic.
Nayden was sorted to the Kask House. Just like before, he kept his wolf-ish secret hidden with help from the professors, allowing him to have a normal school life. He befriended his roommates, Luca and Cristi. Through the two of them, he met Siân, Ileana and Emelia. They became friends immediately and formed their little group named "The Aces". It didn't take long before the Aces discovered what he truly is. However, instead of shunning him out or revealing this to the world, they accepted him. Ever since then, their bonds have been unbreakable.
In spite of his intimidating presence which seems to be sending people a don't-mess-with-me-or-I'll-bring-you-a-painful-death message especially when he's annoyed or angered (which seldom happens unless a full-moon is around the corner), Nayden is in fact easy-going, tolerant, and definitely not blood-thirsty (his diet would be an exceptional case though). Being the eldest among the Aces, he's probably the most mature and responsible. He does has his reckless and rebellious moments especially when he's with the Aces - he is a trouble-maker at heart after all - but he'll make sure that the things they do wouldn't bring people severe injury or even death. He has a great sense of humor, that's unknown to most people except the Aces. He's also extremely brave and loyal. With both intelligence and strength, he will - with or without a wand - ensure that you're deader than a doornail, if you mess with his friends.