Lydia: Lord Lyndsay's Inheritance

Lord Lyndsay is dying from an exotic disease. His two children Lydia and James are identical twins and are 17 years old. Upon their father’s death British law states that the estate goes to the eldest son. Therefore, the son inherits everything and his daughter will get nothing, or next to nothing.
James hates country life, finding it so restricting. He wants to be wild, explore, be free and have many adventures. James has a romantic idea about being a sailor, running away to sea, to be a Captain of a ship, however his father has strictly forbidden it and to reinforce his wishes Lord Lyndsay has written a special clause within his Last Will and Testament that if James should abandon his Lordly duties he would be automatically disinherited.
James has a cunning plan, which involves convincing his sister to pretend to be him, which leads to all sorts of funny misunderstandings, embarrassments and trouble. Romance is out of the question if you are a girl pretending to be a boy.
When Lydia is forced, by her wicked half Uncle Rupert, to visit their plantations in the Caribbean all sorts of adventures befall her; including ship wreck and evil pirates (who cannot read…). “Where there be pirates there be treasure an’ a killin’ an’ a thievin’...” “Pirates be the scum of the earth and the sea be the only mistress that is a willin’ to have us.”
Her greatest challenge is when she discovers where her brother is and what her beloved father had been up to whilst visiting the Caribbean islands…
Finally, James and Lydia must return home to celebrate their twenty first birthday before their wicked half Uncle Rupert discovers what James has been doing…