It depends. More than one person can have copyrights in a piece of work. Whenever you’re collaborating with others to create materials, it’s important to talk about and agree in advance on whether the whole product will be jointly owned, whether separate contributions will be separately owned, or whether you’ll have some other arrangement. You may want to consult a legal advisor for assistance.
For more information on copyright and trademark topics, check out our Copyright & Trademark section in TpT U, and consider taking our Copyright & Trademark Quiz!