They never should have met; circumstances brought them together over a tumultuous situation. His intervention will change their futures.
Her naiveté was an unexpected draw for him, but Jacob's attentions came with a warning, he'd never marry her. Educating her in the ways of the sensual world was supposed to enlighten her and give him pleasure.
Sharing her with another man was supposed to break their bond, not release his jealous streak. Accepting he's in love with her will change them forever.