The parent needs their own applicable authorization. The adult child’s result does not decide a separate parent application or grant the parent residence. Two applications that begin on the same day do not finish on the same day, and neither one waits for the other. Each has its own applicant, its own vetting and its own steps, so the household should plan for outcomes arriving separately. Ask, for each person, what the next required step is and who has to take it — that list is far more useful than a single expected completion date.
Plan the household around individual outcomes
Track each person’s actual documents and remaining steps. Do not promise simultaneous completion or treat a family-care need as an automatic exception to the applicable immigration process. Sequence the household’s commitments behind the individual results rather than ahead of them.
A sale of a home, a resignation or an end to a care arrangement made in anticipation of everyone arriving together is difficult to reverse when one case is still open. Where an older parent needs support, arrange that support on a basis that does not depend on residence being granted — visits under whatever authorization actually exists, or care arranged where the parent is now. Confirm what each person is presently authorized to do before travel is booked, since permission to enter, permission to remain and permission to reside are separate questions.