Reviewers here left out Amber's origins

The book hints that the Earl of Radcliffe's lost love (not his first Countess, whom he was suspected of murdering) was Amber's mother. The resemblance is what drew Radcliffe to Amber when he saw her. But of course, she had no idea.

A little late replying, but yes, in the movie it is heavily implied Amber is the daughter of royalists who left her at the door of a peasant house in the hopes of saving her life after their manor is sacked and burned by Parliamentarians. The child narrowly escapes, while the father is shot moments later. The blanket bearing the fanciful name "Amber" is her only link to her past...peasant family's favored simple, Biblical names, and good common English names.

This is a condensation of an extensive prologue in the book. Please be aware that spoilers follow:

Amber's noble mother lady Judith of a royalist family is betrothed to marry a handsome man from another family of fortune. She grows to love her betrothed despite that theirs is an arranged match, but their wedding plans are shattered by the outbreak of Civil War which finds him on the opposite side. She is subsequently betrothed to the Earle of Radcliffe, who, as we know, later becomes Amber's husband. She detests the Earle, and continues to meet her beloved in secret. He meets her in secret, lays with her, and impregnates her. He sends word that her family's manor will be besieged, and arranges for her to meet him on the eve of the attack to elope with him. Judith's mother catches her in the act, says that she will tell her father that she has been abducted and murdered in the siege rather than have her disgrace known, and banishes her from the family forever. Amber's father places Judith in the care of a charitable peasant family and returns to the fray before he can legitimize the match and is never heard from again. Judith dies in childbirth, but not before she names the child "Amber" for her father's bewitching eyes (which Amber inherits from him). The peasant farmers have grown to love Judith like family, and resolve to raise the orphaned Amber as their own, until such time as her father comes to claim her. He never does, of course, and she grows up as their niece.

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