I read this novel several times as a kid but I can't remember the name of it today. From what I can remember, here are some details:
Probably an early 90s or late 80s fantasy novel.
There was a matriarchal society, women ruled and princes were considered useless to be married off
The two main characters were a silver-haired prince and he was to wed a red-haired woman.
I believe her name was something like "megarea" or "megaria" but I could be wrong. The prince's name is less clear to me, but "crispen" or something that starts with a c sounds about right.
The woman hated the man and resented having to marry him. She saw men as weaklings, and often called him 'best-bethrothed' or something like that in a spiteful way. Only at the end of the novel did she come to tolerate him more.
They were put in charge of running an island, and had to survive there. Most of the novel, or at least the latter half, took place on that island. There were lots of details about how they improved its infrastructure, had better methods of growing food, etc.
There was a scene where they travelled to that island and there was a storm and a mage protected the ship during the storm.
The name might have had 'sunset' or some similar word in it.
That's about all I can remember, sorry. I did like it and read it at least twice, but I can't remember its name at all. Thanks for any help anyone can give!