Avi K…
my answer is not meant to be an enigma. The problem is the choice of words used by the OP.
There is a difference between ‘successfully marry’ and having a successful marriage.
The mere completion of a legal marriage ceremony means that the participants have successfully married. They have accomplished the stated goal going from two single individuals to one married couple.
If, OTOH the OP meant is their only one person with whom each individual can have a successful long term marriage that is a different question.