Black Sheep by Georgette Hayer

Abigail Wendover has no time for love.

She is far too busy protecting her niece, who has fallen madly in love with a suspected fortune-hunter.

But her efforts become vastly more complicated with the arrival of Miles Calverleigh, the black sheep of his family - a reckless bachelor with a scandalous past.

Abby soon discovers that, despite successfully managing her niece's love life, she has far less control over her own unruly heart.