Question: Who was the grandfather of the man confined to the American coastal pentagonal bastion fort known for its role in the War of 1812?

Context paragraphs:
Antwerp Citadel: Antwerp Citadel (Spanish: "Castillo de Amberes" , Dutch: "Kasteel van Antwerpen" ) was a pentagonal bastion fort built to defend and dominate the city of Antwerp in the early stages of the Dutch Revolt.  It has been described as "doubtlesse the most matchlesse piece of modern Fortification in the World" and as "one of the most studied urban installations of the sixteenth century".

Fort Morgan (Alabama): Fort Morgan is a historic masonry Pentagonal bastion fort at the mouth of Mobile Bay, Alabama, United States.  Named for Revolutionary War hero Daniel Morgan, it was built on the site of the earlier Fort Bowyer, an earthen and stockade type fortification involved in the final land battles of the War of 1812.  Construction was completed in 1834 and it received its first garrison in March of the same year.

Fort Victoria (Isle of Wight): Fort Victoria is a former military fort on the Isle of Wight, England (grid reference [ SZ339898] ), built to guard the Solent.  The earliest fort on the site was a coastal fort known as Sharpenode Bulwark built in 1545-7 by Henry VIII, but these defences had fallen into disrepair by the 17th century.  Fort Victoria was built in the 1850s.  It was a brick-built triangular fort with two seaward batteries meeting at a right angle.  It remained in use until 1962.  Parts of the fort were subsequently demolished, and what remains has become part of Fort Victoria Country Park.

Fort Warren (Massachusetts): Fort Warren is a historic fort on the 28 acre Georges Island at the entrance to Boston Harbor.  The fort is pentagonal star fort, made with stone and granite, and was constructed from 1833–1861, completed shortly after the beginning of the American Civil War.  Fort Warren defended the harbor in Boston, Massachusetts, from 1861 through the end of World War II, and during the Civil War served as a prison for Confederate officers and government officials.  The fort remained active through the Spanish–American War and World War I, and was re-activated during World War II.  It was permanently decommissioned in 1947, and is now a tourist site.  It was designated a National Historic Landmark in 1970 as a masterpiece of coastal engineering of the pre-Civil War period, and for its role in the Civil War.  It was named for Revolutionary war hero Dr. Joseph Warren, who sent Paul Revere on his famous ride, and was later killed at the Battle of Bunker Hill.  The name was transferred from the first Fort Warren in 1833, which was renamed Fort Winthrop.

Frank Key Howard: Frank Key Howard (1826 - 1872) (also cited as Francis Key Howard) was the grandson of Francis Scott Key and Revolutionary War colonel John Eager Howard.  Howard was the editor of the "Daily Exchange", a Baltimore newspaper sympathetic to the Southern cause.  He was arrested without a warrant just after midnight on September 13, 1861 at his home by U.S. Major General Nathaniel Prentice Banks on the direct orders of General George B. McClellan enforcing the policy of President Abraham Lincoln.  (In his book he writes that he was told by the arresting officer that the order had come from Secretary of State William Seward.)  The basis for his arrest was for writing a critical editorial in his newspaper of Lincoln's suspension of the writ of habeas corpus, and criticizing the fact that the Lincoln administration had declared martial law in Baltimore and imprisoned without charge George William Brown, the mayor of Baltimore, sitting U.S. Congressman Henry May, all the police commissioners of Baltimore, and the entire city council.  Lincoln's suspension of habeas corpus in Maryland had already been declared unconstitutional by U.S. Supreme Court Chief Justice Roger Taney (Howard's great-uncle by marriage) in Ex parte Merryman, but Lincoln had ignored the federal court ruling.  Howard was initially confined to Fort McHenry, the same fort his grandfather Francis Scott Key saw withstand a British bombardment during the War of 1812, which inspired him to write The Star Spangled Banner, which would become the national anthem of the United States of America.  He was then transferred first to Fort Lafayette in Lower New York Bay off the coast of Brooklyn, then Fort Warren in Boston.

Fort McHenry: Fort McHenry, in Baltimore, Maryland, is a historical American coastal pentagonal bastion fort best known for its role in the War of 1812, when it successfully defended Baltimore Harbor from an attack by the British navy from the Chesapeake Bay September 13–14, 1814.  It was first built in 1798 and was used continuously by U.S. armed forces through World War I and by the Coast Guard in World War II.  It was designated a national park in 1925, and in 1939 was redesignated a "National Monument and Historic Shrine".

Fort Pickens: Fort Pickens is a pentagonal historic United States military fort on Santa Rosa Island in the Pensacola, Florida, area.  It is named after American Revolutionary War hero Andrew Pickens.  The fort was completed in 1834 and remained in use until 1947.  Fort Pickens is included within the Gulf Islands National Seashore, and as such, is administered by the National Park Service.

Fort Shelby (Michigan): Fort Shelby was a military fort in Detroit, Michigan that played a significant role in the War of 1812.  It was built by the British in 1779 as Fort Lernoult, and was ceded to the United States by the Jay Treaty in 1796.  It was renamed Fort Detroit by Secretary of War Henry Dearborn in 1805.  The fort was surrendered to the British by William Hull in 1812, and reclaimed by the Americans in 1813.  The Americans renamed it Fort Shelby in 1813, but references to "Fort Detroit" relating to the War of 1812 are to this fort, not to the earlier Fort Detroit, which had been abandoned by the British in 1779 in favor of Fort Lernoult.  It was given to the city of Detroit in 1826 and dismantled in 1827.

Fort Independence (Massachusetts): Fort Independence is a granite bastion fort that provided harbor defenses for Boston, Massachusetts.  Located on Castle Island, Fort Independence is one of the oldest continuously fortified sites of English origin in the United States.  The first primitive fortification, called "The Castle", was placed on the site in 1634 and, after two re-buildings, replaced circa 1692 with a more substantial structure known as Castle William.  Re-built after it was abandoned by the British during the American Revolution, Castle William was renamed Fort Adams and then Fort Independence.  The existing granite fort was constructed between 1833 and 1851.  Today it is preserved as a state park and fires occasional ceremonial salutes.  Fort Independence was added to the National Register of Historic Places in 1970.

Arippu fort: Arippu Fort (Sinhalese: අරිප්පු බලකොටුව ; Tamil: அரிப்புக் கோட்டை , also known as Allirani fort; Tamil: அல்லிராணிக் கோட்டை ) was built by the Portuguese and was handed over to the Dutch in 1658.  The small bastion fort is located in Arippu, which is 16 km away from Mannar Island.  The fort is nearly square in shape, with two bastions.

Supporting paragraphs: Frank Key Howard Fort McHenry
Answer: Francis Scott Key