Lucky are those that are both the first and last love of each other.
The first part, the man is lucky because he has something very precious in his life being her first love and the second part, both are lucky because if the woman is the last love of a man, I take it that he is also her last love. (reading between the lines here) Example: If I am to be my husbands last love, therefore he is to be mine. However it is so natural to read things in our own way. ~ Brigitte Nicole