Two interesting alternative successions as listed by Wikipedia in regards to the Jacobite claim:
However, it seems all roads still lead to the current Queen Elizabeth in the end.
While Franz, Duke of Bavaria, is the most universally acknowledged Stuart heir there are two others. If one discounts the marriage of the Duke of Bavaria's ancestress Maria Beatrice of Savoy as being invalid in British law (she married her uncle) then the succession would have passed from her to her younger sister Maria Teresa who married the Duke of Parma. Her representative today is HRH The Infanta Alicia, dowager Duchess of Calabria (b. 1917) and mother of the heir of the Kingdom of the Two Sicilies.
The second alternative succession is rather suprising to many. In the book
The Highland Clans, by The Honourable Iain Moncreiffe of that Ilk it is stated that "by the fourteenth century it had become common law [in both England and Scotland] that a person who was not born in the liegeance of the Sovereign, nor naturalized, could not have the capacity to succeed as an heir. He was in the strictest sense "illegitimate," though not of course born out of wedlock. This legal incapacity of aliens to be heirs applied to all inheritances, whether honours or lands.
The effect of the succession opening to a foreigner was that, if he had not been naturalized or if his case was not covered by some special statute, the succession passed to the next heir "of the blood," who thus became the only "lawful" heir. It was of course always open to the Sovereign to confer an honor or an estate on a foreigner; the rule of law merely prevented aliens from being "lawful heirs" to existing inheritances. This "common law" principle was rigorously applied until the Whig Revolution of 1688 after which it was gradually done away with by the mid-nineteenth century. It was precisely because of this law that Queen Anne found it necessary to pass special legislation naturalizing all alien-born potential royal heirs under the "Act of Settlement" provisions. But, of course, from the Jacobite point of view, no new statute could be passed after 1688, and the old law remained static until the death of Cardinal York [King Henry IX] in 1807.
At that time, Henry IX's nearest heir in blood under this argument was not as is sometimes supposed the King of Sardinia, for he had not the legal capacity to be an heir in Britain, unless naturalized which he was not. The nearest British-born heir of Henry IX would have been, in fact, George III, hence his son could indeed legitimately claim to be a Jacobite monarch as portrayed during the
visit of King George IV to Scotland.
Thus, following this argument, the
de jure and legitimist heir to the crown of Great Britain would, ironically, be the
de facto sovereign
Elizabeth II of the United Kingdom.