In The Giver, there is a Committee of Elders that decides the husband-wife pairings for the community. A list of characteristics for each person is considered, and people are matched by the committee according to what appears to be the greatest chance of compatibility. There is no mention of divorce or separation in The Giver.
This is quite different from modern day society, where each person is free to find their own mate through the trial-and-error system of dating. Our society is also different because some of our attraction is fueled by sexuality and hormones, while in The Giver sexuality is negated and procreation is not a part of a marriage.
In our modern Western society, finding a mate is typically a matter of searching for a person who we view positively and romantically as someone we want to spend our life with. This process usually begins after puberty, with young people beginning to explore their feelings through friendship, dating, and eventually sexual exploration; this can involve seeing multiple people, making mistakes, getting your heart broken, falling in and out of love, and learning to deal with the very real joys and hardships of being intimately connected to another human being. Marriage is viewed as a matter of love--a worthy pursuit that involves effort, commitment, and loyalty.
In Jonas's society, the free will associated with relationships is stripped away. Mates are paired based upon clinical views of compatibility, with the decision of who will be matched with who being made by the Committee of Elders. All sexual urges are repressed through the use of medication, and sex, attraction, and procreation are not components of a marital relationship. Ultimately, this is not a process at all, but rather another ceremonial aspect of living in the community.
I am in the eight grade and my class has been reading this book for two months now, and I was looking for this answer and I found out that the Elders are giving the people their mates. I love this book.<3