Currently clans can offer marriage proposal for a female clan member but there is no benefit to giving them up on the contrary we have reasons to keep them as governors and party leaders especially for calling up armies of parties. Clan's should offer money probably based upon clan tier for the bride. These clans gain potential for a party leader and pregnancies that can create more party leaders. Another benefit is the increase in relation through marriages could mean that these clans are more likely to join the player faction because of the marriage or marriages. New dialogue options because of the joining of clans through marriage.
This scene says it all.
This scene says it all.