A person does not have a copyright on his or her own life. Anyone may write a biography of a person, or a story about that person, whether aimed at an adult audience or at any other age group, and no permission from the subject is required.
If the story is about a living artist, and you want to illustrate it with pictures by that artist, those pictures are almost surely protected by copyright. You will need permission to use them unless your use falls under fair use (in the US) fair dealing (in the UK or any of several other countries) or another exception to copyright. Whether an exception to copyright applies. Short quotes used with attribution in such a book are very likely to fall under fair use or fair dealing. Fair use is a somewhat complex and highly fact-driven determination. See Does Fair Use of copyright apply to educational youtube channels?, Is the source important for fair use?, and Is this copyright infringement? Is it fair use? What if I don't make any money off it? for more on fair use in particular.
One thing to be careful of when writing about a living person is defamation (aka libel and slander). If factual statements are made about a person that are false, and that harm that person's reputation, the person may be able to sue and win damages. Even in a work of fiction, if a real person is named, or is used under an alias but is clearly identifiable, and if reasonable people are likely to believe that the statement is about the real person, then a defamation suit could be successful. However, statements of opinion do not lead to defamation liability, at least not under US law. See also this thread and this law.se thread
Copyright protects the right to make copies of a work, the right to distribute copies of the work, the right to make works based on the original work (such as translations, adaptations, and sequels). These last are known as derivative works. It also protects rights to perform and display the work. It does not grant an author or a subject the right to prevent someone from creating a different work about the same topic.