An Unsuitable Alliance by Fenella J. Miller

An Unsuitable Alliance is the first of a six book Regency series, The Earl’s Disputed Inheritance.

Edward Revere is the business partner of identical twins Adam and Richard Somiton and like his friends has no wish to remove himself to Somiton whilst the lawyers decide if Adam is the true Earl of Somiton.
Lady Eleanor Somiton is only too happy to move to the Dower House with her mother, the Countess Somiton and her sister Lady Grace and leave the new incumbents to live in the vast uncomfortable ancestral home.
As all the distant branches of the Somiton family gather for a summer house party not all of them are there with good intentions.
Edward and Eleanor are drawn to each other but they both know such an unsuitable alliance is impossible.