There are 3 books in the Legacy Series series. The newest book is The Valentine Legacy which came out in 1995.

1
The Wyndham Legacy

Book cover of The Wyndham Legacy
A reluctant earl matches wits with an illegitimate heiress in the first novel of the Legacy Trilogy by #1 New York Times bestselling author Catherine Coulter.

Marcus Wynham is passionate, quick to rage, and just as quick to laughter. He’s tough, opinionated, domineering, and known as the devil’s own son.…
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2
The Nightingale Legacy

The Nightingale Legacy
On the eve of her nineteenth birthday, Caroline Derwent-Jones escapes the obsessive attentions of her guardian, Mr. Ffalkes, only to be drawn to the mysterious and reclusive Frederic North Nightingale, Lord Chilton, in a romance set in Regency Cornwall.

3
The Valentine Legacy

The Valentine Legacy
The author of The Nightingale Legacy and The Wyndham Legacy presents the conclusion of her best-selling trilogy, in which antagonists Jessie Warfield and James Wyndham marry and set off to search for Blackbeard's treasure.