Sos says: "Magic is supposed to be mysterious and we don't reveal the secret to others, especially those who are not magicians. My father taught me most of the tricks. He is practically the only one willing to teach me all he knows. I am very lucky to learn some tricks from other magicians, but occasionally I have to trade tricks with them."
Growing up around conjuring, both boys started practising magic tricks at a very young age. Tigran says: "I was four and Dad showed me how to make a card appear and disappear. I was fascinated and wanted to learn more."
The Petrosyan brothers are crazy about magic and exceptionally good at it. Making cards and balls appear out of nowhere, floating a piece of paper in the air and changing into another outfit simultaneously are routine performances for them.
Sos won the Merlin Award, aged 13, in 2009 - the most prestigious award for magicians. Tigran was nominated for the award this year and, at 11, is famous in their home country, Germany.
Sos says: "My standard magic practice time is an hour a day, but I often spend more than that. Whenever I have free time I will work on my card tricks and other tricks. I love magic and have so much fun with it,"
Despite their young ages, the brothers perform like professionals on stage. Always smiling and moving with confidence, they get their audiences actively involved; it is as if they were born for the stage.
The boys' father, Sos Petrosyan Snr, says they have been playing with magic since they were four and conjuring has now become a part of them. Sos Snr says: "When other children are playing with toys, the boys are playing magic tricks. It is in their blood. Many magicians are amazed by the boys' confidence on stage because they never show any signs of stage fright. Even when they made a mistake, they are able to move on to the next trick with total confidence."
Sos Jnr's favourite trick is "Manipulation", where he makes things disappear, then reappear. "Every trick I do I work hard on it for a long time. To be honest there is no trick that I can say is easy to do," he says.
From performances at shopping malls, in competitions and on television talent shows, the brothers have followed their parents by performing on stages around the world.
To cope with performances, taking time off from school is unavoidable. Sos Jnr says: "We try our best to perform during summer holidays, like this trip to Hong Kong, but sometimes we need to miss school. At first schoolmates were curious about my absence. But now they are used to it; when they don't see me in class they know I am on the road giving a show."
In many performances, the brothers act as side-kicks for their parents, but they were planning to be the main act yesterday at Fashion World, at the Wonderful Worlds of Whampoa.
Tigran says: "It will be the first time my brother and I give the main performance while our parents play the supporting role. I am really happy and excited about it."