Ai giàu ba họ, ai khó ba đời, Thế gian rồi sẽ đổi đời cho coi.

Who is three families-rich, who is three generations-poor, The world then will see life change.

This is describing how life is full of changes and nothing is forever. A person has three families (father’s, mother’s, and spouse’s families). This is equivalent to “There’s never a road without a turning” (i.e., no situation in life is forever).