Ferdinand VI of Spain
Ferdinand VI of Spain( 23 September 1713 – 10 August 1759), called the Learned(" el Prudente") and the Just(" el Justo"), King of Spain from 9 July 1746 until his death in 1759, was the third ruler of the Spanish Bourbon dynasty.
He was the fourth son of the previous monarch Philip V and his first wife Maria Luisa of Savoy.
Maria Luisa of Spain
Infanta Maria Luisa of Spain( Spanish:" María Luisa", German:" Maria Ludovika")( 24 November 1745 – 15 May 1792) was Holy Roman Empress, German Queen, Queen of Hungary and Bohemia, Grand Duchess of Tuscany as the spouse of Leopold II, Holy Roman Emperor.
Maria Luisa, Duchess of Lucca
Maria Luisa of Spain  (6 July 1782 – 13 March 1824) was a Spanish infanta, daughter of King Charles IV and his wife, Maria Luisa of Parma.
In 1795, she married her first cousin Louis, Hereditary Prince of Parma.
She spent the first years of her married life at the Spanish court where their first child, Charles, was born.
In 1801 the Treaty of Aranjuez made her husband King of Etruria, a kingdom created from the former Duchy of Tuscany in exchange for the renunciation of the Duchy of Parma.
They arrived in Florence, the capital of the new kingdom, in August 1801.
During a brief visit to Spain in 1802, Maria Luisa gave birth to her second child.
Her husband's reign in Etruria was marred by his ill health.
He died in 1803, at the age of 30, following an epileptic crisis.
Maria Luisa acted as regent for their son.
During her government in Florence, she tried to gain the support of her subjects, but her administration of Etruria was cut short by Napoleon Bonaparte, who forced her to leave with her children in December 1807.
As part of the Treaty of Fontainebleau, Napoleon incorporated Etruria to his domains.
After a futile interview with Napoleon in Milan, Maria Luisa looked for refuge in exile with her family in Spain.
The Spanish court was deeply divided and a month after her arrival the country was thrown into unrest when a popular uprising, known as the Mutiny of Aranjuez, forced Maria Luisa's father to abdicate in favor of her brother Ferdinand VII.
Napoleon invited father and son to Bayonne, France, with the excuse of acting as a mediator, but gave the kingdom to his brother Joseph.
Napoleon called the remaining members of the Spanish royal family to France and at their departure on 2 May 1808, the citizens of Madrid rose up against the French occupation.
In France, Maria Luisa was reunited in exile with her parents.
She was the only member of the Spanish royal family to directly oppose Napoleon.
After her secret plan to escape was discovered, Maria Luisa was separated from her son and placed with her daughter as prisoners in a Roman convent.
Maria Luisa, mostly known as the Queen of Etruria during her lifetime, regained her freedom in 1814 at the fall of Napoleon.
In the following years she continued to live in Rome, hoping to recover her son's former domains.
To put forward her case she wrote a book of memoirs, but was disappointed when the Congress of Vienna (1814–15) compensated her not with Parma, but with the smaller Duchy of Lucca, which had been carved out of Tuscany.
As a consolation she was allowed to retain the honors of a queen.
Initially reluctant to accept this accord, Maria Luisa did not take the government of Lucca until December 1817.
As a reigning duchess of Lucca, she disregarded the constitution imposed by the Congress of Vienna.
While spending time in her palace in Rome, she died of cancer at the age of 41.
Archduchess Maria Luisa of Austria, Princess of Tuscany (1798-1857)
Archduchess Maria Luisa of Austria, Princess of Tuscany( 30 August 1798 – 15 June 1857) was a member of the House of Habsburg- Lorraine.
Princess Maria Luisa of Savoy (1729–1767)
Maria Luisa of Savoy (Maria Luisa Gabriella; 25 March 1729 – 22 June 1767) was a princess of Savoy.
Infanta Luisa Fernanda, Duchess of Montpensier
Infanta María Luisa Fernanda of Spain, Duchess of Montpensier( 30 January 1832 – 2 February 1897) was Infanta of Spain and Duchess of Montpensier.
She was the youngest daughter of King Ferdinand VII of Spain and his fourth wife Maria Christina of the Two Sicilies, the queen- regent, who was also his niece.
Infanta Margarita, Duchess of Soria
Infanta Margarita of Spain, Duchess of Soria, 2nd Duchess of Hernani, Grandee of Spain(" Margarita María de la Victoria Esperanza Jacoba Felicidad Perpetua de Todos los Santos de Borbón y Borbón"; born 6 March 1939), is the younger sister of King Juan Carlos and aunt of the reigning King Felipe VI of Spain.
Maria Luisa of Parma
Maria Luisa of Parma (9 December 1751 – 2 January 1819) was Queen consort of Spain from 1788 to 1808 by marriage to King Charles IV of Spain.
She was the youngest daughter of Philip, Duke of Parma, the fourth son of Philip V of Spain and Louise Élisabeth of France, the eldest daughter of King Louis XV.
Maria Luisa of Savoy
Maria Luisa of Savoy (Maria Luisa Gabriella; 17 September 1688 – 14 February 1714) was a queen consort of Spain by marriage to Philip V of Spain.
She acted as Regent of Spain during the absence of her spouse from 1702 until 1703, and had great influence over him as his adviser, while she was herself in turn influenced by the Princesse des Ursins.
Archduke Joseph, Palatine of Hungary
Joseph Anton Johann, Archduke of Austria( 9 March 1776, Florence – 13 January 1847, Buda), was the Palatine of Hungary from 1796 to 1847.
He was the seventh son of Leopold II, Holy Roman Emperor and Maria Luisa of Spain.

Question: Who is Maria Luisa, Duchess Of Lucca's maternal grandfather?
Answer: Philip, Duke of Parma