Justin and Hailey Bieber are tying the knot again -- but this time, they're doing it in the sunshine and inviting a bunch of their friends and family, including another very famous couple ...TMZ has learned.

Sources familiar with the planning shared that J.B. and H.B.'s wedding is taking place during the weekend of March 1 -- which also happens to be Justin's 25th birthday. This is no coincidence -- we're told Justin wanted to be a "married" man by his next birthday.

TMZ Sources said the 2nd round of nuptials are taking place somewhere in L.A. While the Biebers' families are primarily located in the East Coast and Canada -- where they initially wanted to have the wedding -- they ultimately changed their minds because the weather sucks.

So wedding #2 has moved out West, and it will be a religious affair since #1 was not performed in the eyes of God.

Two people who've already received a "Save the Date" email -- Kylie Jenner and Travis Scott.