Wait(NULL) question

For example, if I have a series of processes as follows,
P1 fork P2
P2 fork P3
P3 fork P4.

I call wait(NULL) in P3, P2 and P1 before terminating them.
So when P4 terminates, is the order of termination P3, P2 then P1??
Will wait(NULL) be affected by other processes' termination other than its own child?

> Will wait(NULL) be affected by other processes' termination other than its own child?
P1 can't terminate before P4, because there is a chain of wait()'s going on.

So it will terminate in P4 P3 P2 P1 order.