whats the relationship between Carl and alexandra?

At the start of the novel, the Linstrums own the farm next to the Bergsons' homestead, and their teenage son, Carl, establishes a special bond with Alexandra Bergson. When Carl returns to the Divide as an adult, his friendship with Alexandra evolves into a deeper attraction. At the novel's end, they resolve to marry.

There's a great analysis right here on gradesaver for Part II, chapters v-xii

that includes a close look at Carl and Alexandra's relationship. Follow the link below;