Hey team, I have a question about my in laws visitors visa (recently approved)

Father in law is the principal applicant, non principal applicant is mother in law.
can my mother in law (non principal applicant) arrive in nz first without the principal applicant?

Example. Mother in law arrives in January, 2023 father in law arrives in march 2023. They both leave nz together in April 2023.

Pls advise, I have been trying to get hold of INZ to no avail.