Which character does Harper choose to develop least in the story?

Laura

Janette

Laura's husband

Laura's brother

If by "least developed" you mean as the one who was barely mentioned, it is Laura's brother. The only time was when she was close to dying, her brother was there to accompany Laura in going home. But Laura's husband, he was still the man he was when he married Laura, selfish and a man with a sad past. He was only hiding his true self and it shows as the years passed, for he had abandoned Laura and became a drunkard. When Laura was on her deathbed, he didn't bother at least showing up for the last time.