Jonker was born to No-Maj parents. His father was a successful cabinet maker, which presumably gave him early experience with wood-working, and allowed him to become a skilled wandmaker in his own right. Jonker's wands were in great demand and could be easily identified by the mother-of-pearl inlay they typically contained. Jonker experimented with several different wand cores before settling on hair of the Wampus cat as his preferred kind.
- The surname "Jonker" is a variation of the Netherlands title "jonkheer", meaning "young lord", and can be a honorific or occupational surname indicating an ancestor that served a jonkheer.
Behind the scenes
- As a Muggle-born, it is unknown how, or if, he was recruited to Ilvermorny School of Witchcraft and Wizardry because of Rappaport's Law restriction on the interaction of wizards with his muggle family.
- Pottermore (Mentioned only)
- Fantastic Beasts and Where to Find Them (film) (mentioned on wand permit application)