Marriage in the Roman Empire

My image of the Roman empire is negative.  The sole purpose of marriage in Rome was for two citizens to produce sons who would inherit their father's property.  The "legitimate" marriages were exclusive to citizens, and marriages that were not legitimate was considered inferior to the legitimate marriages.  The children born out of a marriage that was not legitimate were also considered inferior to those who were born out of a legitimate marriage.  In the case of marriages, or contuberniums between slaves, there was no guarantee that the husband and wife would stay together afterwards, because the owner still had the right to sell them.  Any children they bore would also be born into slavery.  The exclusiveness of legitimate marriage was unfair to everyone who wasn't a citizen, as they weren't allowed to show their commitment to another person in a legitimate way.  Also, the limitations imposed on girls and women in marriage were unfair.  Girls were betrothed at an age as early as seven years old, when they wouldn't even know what a marriage was.  Their fathers usually arranged their marriages, and they weren't allowed to choose whom they wanted to marry.  Women also faced injustice in divorce, because the children would automatically belong to the father.  Laws passed by Constantine also gave women more penalties for divorce, such as being deported to an island, while men simply had to return the dowry to the ex-wife.  Marriage in Rome was overall unjust in that it was exclusive to citizens and gave limited options to women.