Past Perfect by Danielle Steel

Sybil and Blake Gregory live a predictable Manhattan life — she as a cutting-edge design authority and museum consultant, he in high-tech investments — raising their teenagers Andrew and Caroline and six-year-old Charlie. But when Blake is offered a dream job as CEO of a start-up in San Francisco, he accepts it, without consulting his wife, and buys a magnificent, historic mansion as their new home in Pacific Heights.

Past and present collide at their elegant mansion, when they meet the large and lively family who lived there a century ago. All long dead but very much alive in spirit—visible to the Gregorys and no one else. Have the Gregorys been given a perfect gift; beloved friends, a chance to relive the past and the wisdom and grace to shape the future?