Dorothy Sidney, Countess of Leicester
Her sister was the alleged intrigant Lucy Hay , Countess of Carlisle , and their eldest surviving brother was Algernon Percy , 10th Earl of Northumberland . 
<triplet> Lucy Hay, Countess of Carlisle <subj> Algernon Percy, 10th Earl of Northumberland <obj> sibling <triplet> Algernon Percy, 10th Earl of Northumberland <subj> Lucy Hay, Countess of Carlisle <obj> sibling