The mob boss of the Marci Family had told them, before-then fourteen year olds Harry and Hermione that they had magic, and that magic indeed existed. They rarely use magic unless it helped them get away from the law or annoying assholes trying to murder them. They have made quite a few enemies growing up and working for shady characters, most of them muggle, but only a few magical. It was the magical hit-men they fought with magic to survive. Guns helped, too. But in secret and in the privacy of several safe houses they found and made their own in several cities across Europe, they practice on using their magic. They didn't have to restrict themselves to wands, but wands helped from the few wizards that track them down just to kill them for practicing. Yes, they can use a form of wandless magic.