While I understand the controversy surrounding the main characters' child's creation, it's fictitious and may not have been intended for literal interpretation, kind of like in Fifty Shades.
Heather and Brandon's relationship is comparable to Scarlett and Rhett in Gone with the Wind and Blair Waldorf and Chuck Bass in Gossip Girl. Treating the act that led to Heather becoming with child as symbolism, I appreciate her and her husband as an example of people making themselves great, a la the aforementioned couples in Gossip Girl and Fifty Shades.
Heather and Brandon sail to his plantation in the Carolinas (which some people disliked due to the antebellum setting), one of the things I loved about the book when I first discovered it, for I was a North Carolina Southern belle when I was a little girl. Setting aside the controversial subject matter at the center of their relationship, I'm glad that despite their ups and downs they ended up with a happy family.