Question: The Grandma of Lucius Antonius was the elder sister of which Emperor ?

Context paragraphs:
Lucius Antonius Naso: Lucius Antonius Naso was an man of ancient Rome who served as tribune of the Praetorian Guard in the year 69, and procurator of the Roman province of Bithynia during the reign of Vespasian.  It is likely he was from Heliopolis (modern Baalbek), as that is where the most notable inscription about his life was found.

Octavia the Younger: Octavia the Younger (69 BC – 11 BC), also known as Octavia Minor or simply Octavia, was the elder sister of the first Roman Emperor, Augustus (known also as Octavian), the half-sister of Octavia the Elder, and the fourth wife of Mark Antony.  She was also the great-grandmother of the Emperor Caligula and Empress Agrippina the Younger, maternal grandmother of the Emperor Claudius, and paternal great-grandmother and maternal great-great grandmother of the Emperor Nero.

Lucius Antonius (grandson of Mark Antony): Lucius Antonius (20 BCE – 25CE) was the eldest son of Iullus Antonius and Claudia Marcella Major.  He was the grandson of triumvir Mark Antony and Octavia (sister of Augustus).  No other siblings are known, but some epigraphic evidence suggests he had either a sister or a daughter Iulla Antonia.  His maternal half-sister was Vipsania Marcella.

Lucius Antonius (brother of Mark Antony): Lucius Antonius (1st century BC) was the younger brother and supporter of Mark Antony, a Roman politician.

Lucius Antonius: Lucius Antonius is a combination of "praenomen" and family name "(nomen)" used by ancient Roman men from a plebeian branch of the "gens Antonia," including:

Perusine War: The Perusine War (also Perusian War or War of Perusia) was a civil war of the Roman Republic, which lasted from 41 to 40 BC.  It was fought by Lucius Antonius and Fulvia to support Mark Antony against his political enemy (and the future Emperor Augustus), Octavian.

Marcus Antonius Creticus: Marcus Antonius Creticus (flourished 1st century BC) was a Roman politician, member of the Antonius family.  Creticus was son of Marcus Antonius and, by his marriage to Julia Antonia, he had three sons: Triumvir Marcus Antonius, Gaius Antonius and Lucius Antonius.

Lucius Antonius Saturninus: Lucius Antonius Saturninus was a Roman Senator and general during the reign of Vespasian and his sons.  While governor of the province Germania Superior, motivated by a personal grudge against Emperor Domitian, he led a rebellion known as the Revolt of Saturninus, involving the legions Legio XIV Gemina and Legio XXI Rapax, camped in "Moguntiacum" (Mainz).

Domitia Lepida the Younger: Domitia Lepida, also known as Domitia Lepida the Younger, or Domitia Lepida Minor , (c. 5 BC - 54 AD); was the younger daughter of consul, Lucius Domitius Ahenobarbus and Antonia Major.  Her elder sister was Domitia Lepida the Elder and her younger brother was Gnaeus Domitius Ahenobarbus, father of the Emperor Nero.  She was the great niece of Emperor Augustus, granddaughter of Octavia the Younger and Triumvir Mark Antony, second cousin to the Emperor Caligula, first cousin and mother-in-law to the Emperor Claudius and paternal aunt of the Emperor Nero.  Lepida was a beautiful and influential figure.  Like her sister, she was also very wealthy.  She had holdings in Calabria and owned the "praedia Lepidiana".

Iulla Antonia: Iulla Antonia or Julia Antonia, is thought to be a daughter of Roman consul of 10 BCE Iullus Antonius and Claudia Marcella Major.  Her brother was Lucius Antonius.  Possible maternal half-siblings include Vipsania Marcella, Appuleia Varilla, and Lucius Antonius.  The only evidence of her existence is a funerary urn.

Supporting paragraphs: Lucius Antonius (grandson of Mark Antony) Octavia the Younger
Answer: Augustus