Question: Who is Titus Junius Brutus's paternal grandfather?

Context paragraphs:
title: Junius Brutus Booth
paragraph_text: Junius Brutus Booth( May 1, 1796 – November 30, 1852) was an English stage actor. He was the father of actor John Wilkes Booth, the assassin of U.S. President Abraham Lincoln. His other children included Edwin Booth, the foremost tragedian of the mid-to- late 19th century, Junius Brutus Booth Jr., an actor and theatre manager, and Asia Booth Clarke, a poet and writer. Booth was named after Marcus Junius Brutus, one of the lead assassins in William Shakespeare's tragedy" Julius Caesar".
title: Decimus Junius Brutus Callaicus
paragraph_text: Decimus Junius Brutus Callaicus( or Gallaecus or Callaecus)( 180 BC113 BC) was a consul of the Roman Republic for the year 138 BC together with Publius Cornelius Scipio Nasica Serapio. He was an optimate politician and a military commander in Hispania and in Illyria. He was the son of Marcus Junius Brutus( consul in 178 BC) and brother of Marcus Junius Brutus( praetor in 88 BC). He had a son also named Decimus Junius Brutus( consul in 77 BC) and his grandson was Decimus Junius Brutus Albinus. Decimus Junius Brutus belonged to the optimates, a political faction which supported the interests of the aristocracy and was opposed to both the plebeian tribunes( the representatives of the plebs) and populares, a political faction which championed the cause of the poor and wanted reforms to help them. During his consulship he and his colleague P. Cornelius Scipio Nasica opposed the plebeian tribunes. The plebeian tribune Gaius Curiatus sent both consuls to prison because they did not allow the plebeian tribunes to select ten men who would be exempt from military service. The two consuls also opposed a proposal by the tribunes to purchase grain from abroad because the price of grain was going up. Scipio Nasica made a speech which quieted the restless plebs.
title: Lucius Junius Brutus
paragraph_text: Lucius Junius Brutus  was the founder of the Roman Republic and traditionally one of the first consuls in 509 BC. This followed his successful overthrow of the Roman monarchy. He was claimed as an ancestor of the Roman gens Junia, including Decimus Junius Brutus and Marcus Junius Brutus, the most famous of Julius Caesar's assassins.
title: Tiberius Junius Brutus
paragraph_text: Tiberius Junius Brutus( died c. 509 BCE) was the younger son of Lucius Junius Brutus, who was one of Rome's first two consuls in 509 BCE. His mother was Vitellia. At the invitation of his uncles, called Vitellii, he and his elder brother Titus Junius Brutus joined the Tarquinian conspiracy. When the conspiracy was discovered, he and the other conspirators were executed by order of the consuls. Punishment was carried out by the lictors, and included being stripped naked, beaten with rods and then beheaded. Lucius Junius Brutus was admired for his strong stance in ordering the execution of his sons, although at times during the execution he showed his emotions.
title: Tiberius Junius Brutus
paragraph_text: Tiberius Junius Brutus( died c. 509 BCE) was the younger son of Lucius Junius Brutus, who was one of Rome's first two consuls in 509 BCE. His mother was Vitellia. At the invitation of his uncles, called Vitellii, he and his elder brother Titus Junius Brutus joined the Tarquinian conspiracy. When the conspiracy was discovered, he and the other conspirators were executed by order of the consuls. Punishment was carried out by the lictors, and included being stripped naked, beaten with rods and then beheaded. Lucius Junius Brutus was admired for his strong stance in ordering the execution of his sons, although at times during the execution he showed his emotions.
title: Titus Junius Brutus
paragraph_text: Titus Junius Brutus (died c. 509 BC) was the elder son of Lucius Junius Brutus, who was one of Rome's first two consuls in 509 BC. His mother was Vitellia. At the invitation of his uncles, called Vitellii, he and his younger brother Tiberius Junius Brutus joined the Tarquinian conspiracy. When the conspiracy was discovered, he and the other conspirators were executed by order of the consuls. Punishment was carried out by the lictors, and included being stripped naked, beaten with rods and then beheaded. Lucius Junius Brutus was admired for his strong stance in ordering the execution of his sons, although at times during the execution he showed his emotions.
title: Decimus Junius Brutus
paragraph_text: Decimus Junius Brutus may refer to:
title: Sempronia (wife of Decimus Brutus)
paragraph_text: Semprònia was an Ancient Roman woman who was the wife of Decimus Junius Brutus, the consul of 77 B.C. and possibly mother of his son Decimus Junius Brutus Albinus who became one of Julius Caesar's assassins.
title: Decimus Junius Brutus (consul 77 BC)
paragraph_text: Decimus Junius Brutus( fl. 1st century BC) was a Roman politician who was elected consul in 77 BC.
title: Kaya Alp
paragraph_text: Kaya Alp was, according to Ottoman tradition, the son of Kızıl Buğa and the father of Suleyman Shah, who was, in turn, the grandfather of Ertuğrul, and the great grandfather of the Ottoman Empire founder, Osman I.

Reasoning steps:
Titus Junius Brutus father Lucius Junius Brutus
Lucius Junius Brutus father Marcus Junius

Answer: spans: Marcus Junius