Mary Queen of Scots – beheaded
Henry, Lord Darnley – strangled
James I and VI – stroke
Anne of Demark – alcoholism
Henry, Prince of Wales – typhoid
Elizabeth the "Winter Queen" of Bohemia – pleurisy
Charles I – beheaded
Henrietta Maria – accidental opium overdose
Charles James – died a few hours after birth (premature?)
Charles II – mercury poisoning
Catherine of Braganza – appendicitis
Lucy Walters – sexually transmitted disease (?)
James Scott, Duke of Monmouth – beheaded
Duke of Grafton – killed in action
Earl of Plymouth – dysentery
Barbara Villiers, Countess of Castlemaine – dropsy (probably kidney failure or diabetes)
Mary of Orange – smallpox
William II of Orange – smallpox
William III – pneumonia/broken collarbone
James II – stroke/pneumonia
Anne Hyde – cancer (?)
Mary Beatrice of Modena – cancer
Mary II – smallpox
Queen Anne – stroke
William, Duke of Gloucester – scarlet fever
James II’s children (and those of Queen Anne) who died very young – epidemic disease
James III/The Old Pretender – brain tumor
Clementina Sobieska – heart failure
Bonnie Prince Charlie – alcoholism
Henry, Cardinal York – old age (?)
Louise Marie “La Consolatrice” – smallpox
Elizabeth and Anne Stuart – tuberculosis
Henry, Duke of Gloucester - smallpox
Minette d’Orleans – peritonitis
Marie Louise, Queen of Spain – typhoid
Anne Marie of Savoy – old age (?)
Son whose name I can’t remember – epidemic disease
Note: you could add "quacked to death by doctors" to almost everyone on this list and you wouldn't be wrong.
Disclaimer: I don’t teach history.