This is a great question, and not very often do I get to speak on something so specific to my identity. However, I should note that in Haudenosaunee way, I cannot claim to be an "expert" or have my knowledge on this topic be considered to be set in stone. Everything that I can relate will be what I've learned from many elders and traditional teachers and various historical references I've seen.

In order to really understand the concept of Haudenosaunee marriage, a lot has to be taken from traditional values, oral history, the Creation Story, specific words in our languages, and the changes in beliefs and practices over time.

When talking about the creation of humans, it's said that the Creator had made a man and a woman from clay of the earth, and with them, he blew 3 breaths of air into them, giving them life. It's also at this time that it's said that the Creator had gave "original instructions" to all life on earth; Everything has a place and duty, including humans. The Creator had intended that a man and a woman would "put their 2 minds together as one", and gave them the ability to procreate, and are to live together as a loving family in harmony with the earth.

As time moved on, and the Great Law of Peace was established among the original 5 Nations, there was this huge emphasis on it being modeled after the Family structure. It was recognized that since women are the child-bearers, our bloodlines are to now run exclusivley through them to ensure the future of the Nation continues on; Any identity from the father of a child is not carried on (ie. A Seneca Turtle Clan woman and a Mohawk Wolf Clan man have children, the children by virtue are now Seneca Turtle Clan members only).

What also becomes established, is how marriage rites are to be conducted. First, the mothers of both the man and woman are to agree to the marriage proposal, sometimes arranging a possible marriage themselves. Then a ceremony is planned, and both familes are invited to attend. It's here where the marriage is formalized, and gifts are exchanged between the couple symbolizing their offerings to each other. Contrasted by a lot of other culture's practices, a man "marries into" the woman's family, joining her village and living together with her family. Men typically were providers for their family, hunting and laboring. Meanwhile women raised children, cooked and tended to gardens. There's a unique perspective in Haudenosaunee culture that men and women were not seen as "equal" in western terms, but also weren't really placed highly above one another either. Men and Women had specific duties to perform to work together in life. Women being homemakers also doesn't signify that there was a misogynistic presence in their society.

It should be noted that I have seen in one historical research paper, that divorce would be permitted only if the mothers of both parties also agreed to it. However, tradition dictates that marriage is "eternal", and you only have 1 partner for life. In historical instances, it is known that re-marrying occured, so perhaps the stigma of divorce and multiple partners fell out of favor at some point.

In 1799, Seneca Chief Handsome Lake received visions from 4 Beings sent by the Creator, to "straighten the minds of the people". At this time historically, Haudenosaunee people were facing a lot of turmoil as a result of the effects of war and changing social norms from the introduction of Western goods and ideals. Alcoholism was rampant, and the family structure that was originally to be protected was failing.

In this message, called the Gaiwiio, a very large emphasis was placed again on protecting the family, and love and marriage as well. Certain behaviors were condemned (domestic abuse, child abuse, no use of alcohol because of the harmful effects of heavy usage), and also included encouragement of good behaviors (giving instructions on how a man and woman are to talk and treat each other and their children, create families based on good values, be faithful, etc.) among many other topics.

With the Gaiwiio, followers of the message saw a morale boost in the wake of some horrific events, of which are well documented elsewhere. The idea of continuity is picked up again. We start to see the incorporation of parts of the Gaiwiio into marriage ceremonies, in the form of giving instructions to a man and woman how they will spend the rest of their lives in a post-colonial world with outside influences that can be harmful to Haudenosaunee way of life. This is typically the format of marriage ceremonies that still occur today.

In a lot of ways, the reorganization of marriage for Haudenosaunee people has always been about survival and continutity of bloodlines, values, ideals, etc. in the face of great change around them. However, with Love being a foundational value in Haudenosaunee culture, it's always a reoccuring theme in a lot of our history. When you raise good families, your raise strong Nations, and it starts with a strong loving marriage.

It's difficult to fully convey the importance of something like marriage in Haudenosaunee way of life in a few short paragraphs without acknowledging a lot of oral history and undertones often missed by historians who aren't immersed in the culture. I hope this gives you a good understanding of what you asked for! I'd be glad to answer any other questions to the best of my knowledge.