Joshua is endowed, and descended from the Red King's daughter, Lilith and Count Harken Badlock. More of his ancestry are hinted throughout the series. Ashkelan Kapaldi is one of his ancestors, who lived in the seventeenth century. His great great uncle and aunt, Silas and Steffania Sugwash are also mentioned. Joshua's endowment is magnetism. Things cling to Joshua such as dirt, dust, and paper. His magnetism also can cling people to him, in other words, people become his friends. This has happened to Tancred Torsson. Joshua's endowment is proved very powerful when it is combined with telekinesis, helped by the Branko twins. In the sixth book, it is used to drag Charlie forcefully into a dark alley where they interrogate him, which prevents Charlie to be able to move.
Joshua is described to be "not very enthuastic" about being in art. He also doesn't like to practice potion making with his mother, as he thinks it's "horrible". Joshua is also very fond of Manfred Bloor, and would do anything to please him. The Branko twins, Idith Branko and Inez Branko are seen a lot around Joshua at Bloor's Academy. They make fun of Charlie and his friends, and don't get into trouble for it.
In the seventh book, Joshua annoys Charlie in the Corridor of Portraits, when Billy Raven, a victim often tormented by the twins, disappears into the painting of Badlock. Charlie pushes Joshua over and Joshua knocks into a pianting, which falls over him. Unfortunately, it happens to be the portrait of Donatella da Vinci, the Talent Master's great great great grandmother. When Manfred finds out what happens, he sends Charlie to the headmaster who orders Mr. Weedon to lock him in the Grey Room.
Joshua also is friends with Dagbert Endless, and describes him to be like "a best friend". Joshua confesses to Lord Grimwald that the two often stole things, and it would not be a problem to capture Dagbert's sea gold charms for him. He leaves with Mr. Weedon, Mrs. Weedon, Norton and his mom Titania Tilpin.