Question: The Nemean lion was killed by the son of which Greek gods?

Context paragraphs:
Lansdowne Heracles: The Lansdowne Heracles is a Roman marble sculpture of about 125 CE.  Today it is in the collection of the J. Paul Getty Museum's "Getty Villa" in Malibu, California.  The statue, representing the hero Heracles as a beardless Lysippic youth grasping the skin of the Nemean lion with his club upon his shoulder, was discovered in 1790 on the site of Hadrian's Villa in Tivoli, Italy, where many fine Hadrianic copies and pastiches of Greek sculptures had been discovered since the 16th century.  Today, the sculpture is considered to be an example of Roman-era improvisations on the Greek sculptural style of the fourth century BCE than a copy of a specific Greek original.

Nicodamus (sculptor): Nicodamus (Ancient Greek: Νικόδαμος ) was a sculptor from Maenalus (modern Mainalo) in Arcadia, who made statues of the Olympic victors Androsthenes, Antiochus of Arcadia, and Damoxenidas; one of the goddess Athena, in bronze and carrying her helmet and aegis, dedicated by the Eleans; and one of Hercules, as a youth, killing the Nemean lion with his arrows, dedicated at Olympia by Hippotion of Tarentum.

Heracles: Heracles ( ; Ancient Greek: Ἡρακλῆς , "Hēraklēs", from "Hēra", "Hera"), born Alcaeus (Ἀλκαῖος , "Alkaios") or Alcides (Ἀλκείδης , "Alkeidēs"), was a divine hero in Greek mythology, the son of Zeus and Alcmene, foster son of Amphitryon and great-grandson and half-brother (as they are both sired by the god Zeus) of Perseus.  He was the greatest of the Greek heroes, a paragon of masculinity, the ancestor of royal clans who claimed to be Heracleidae (Ἡρακλεῖδαι ), and a champion of the Olympian order against chthonic monsters.  In Rome and the modern West, he is known as Hercules, with whom the later Roman emperors, in particular Commodus and Maximian, often identified themselves.  The Romans adopted the Greek version of his life and works essentially unchanged, but added anecdotal detail of their own, some of it linking the hero with the geography of the Central Mediterranean.  Details of his cult were adapted to Rome as well.

Statue of Hercules strangling the Nemean Lion, Piazza Ognissanti: Statue of Hercules strangling the Nemean Lion, Piazza Ognissanti

Aella (Amazon): Aella - Ἄελλα (often confused with Aello the Harpy) was one of Hippolyte's Amazons in Greek mythology.  She was the first to attack Heracles when he came for Hippolyte's girdle.  Unfortunately, Heracles was wearing the Nemean Lion skin from his first labor, making him invulnerable.  Aella could not kill Heracles; thus, she was killed instead.  Her name means "whirlwind".  Aella must have been strong, for she was one of the small group set aside to fight Heracles.  It was a long and close battle, but eventually, he took her down.  She was known for fighting well with a double-axe.

Nemean lion: The Nemean lion ( ; Greek: Νεμέος λέων "Neméos léōn"; Latin: "Leo Nemeaeus" ) was a vicious monster in Greek mythology that lived at Nemea.  It was eventually killed by Heracles.  It could not be killed with mortals' weapons because its golden fur was impervious to attack.  Its claws were sharper than mortals' swords and could cut through any armor.

Heracles Papyrus: The Heracles Papyrus (Sackler Library, University of Oxford, Pap.  Oxyrhynchus 2331) is a fragment of a 3rd-century Greek manuscript of a poem about the Labors of Heracles.  It contains three unframed colored line drawings of the first of the Labors, the killing of the Nemean Lion, set within the columns of cursive text.  It was found at Oxyrhynchus (Pap.  2331) and is one of the few surviving scraps of classical literary illustration on papyrus.  The fragment is 235 by 106 mm.

Mathura Herakles: The Mathura Herakles is a famous statue found in the city of Mathura, India, thought to represent the Greek hero Herakles fighting the Nemean lion.

Leo (constellation): Leo is one of the constellations of the zodiac, lying between Cancer the crab to the west and Virgo the maiden to the east.  Its name is Latin for lion, and to the ancient Greeks represented the Nemean Lion killed by the mythical Greek hero Heracles (known to the ancient Romans as Hercules) as one of his twelve labors.  Its symbol is (Unicode ♌).  One of the 48 constellations described by the 2nd-century astronomer Ptolemy, Leo remains one of the 88 modern constellations today, and one of the most easily recognizable due to its many bright stars and a distinctive shape that is reminiscent of the crouching lion it depicts.  The lion's mane and shoulders also form an asterism known as "The Sickle," which to modern observers may resemble a backwards "question mark."

Altis: The Altis (Greek: Ἄλτις) also referred to as the sanctuary to the gods, is the name of a location most well known for being a place of significant religious importance to the Ancient Greeks, considered to be a sacred precinct that was constructed and used from around 776 BCE to fourth century BCE and used for the worship of several Greek gods and goddesses.  Though the architects are not definitively known, it is generally attributed to be partially the work of Libon of Elis.  Located in the wide valley of the Alfeiós River (also Romanized as Alpheus, Alpheios) in the western part of Peloponnesus, around 18 kilometers away from the Ionian Sea, the name Altis was derived from a corruption of the Elean word alsos meaning “the grove” because the area was thickly wooded with oaks, plane trees, poplars, and olives.  The structure itself was an irregular quadrangular area more than 200 yards (183 meters) on each side and walled except to the North where it was bounded by the Kronion (Mount Kronos).  Inside were sanctuaries, the centers of religious worship, where the Greeks built over 70 temples, treasuries, altars, statues, and other structures in dedication to their gods.  The site was continuously inhabited from Mycenaean times until the 6th century BCE, where cult activity apparently first began at the foot of the hill of Kronos where altars to the goddesses Rhea, Gaia, and Eileithyia have left their traces.  Some other cults found here were devoted to figures like the hero cult of Pelops and Hippodameia (arguably the oldest shrine there) important mythological figures that are generally known for the founding myth of the Olympic Games.  During the time of the Dorian Invasion settlers from northwestern Greece inhabited the Altis whereby they introduced the worship of two major Greek deities in the Greek pantheon Hera and Zeus as well as constructing the most memorable things there, the Sanctuary and altar of Zeus, where to this day the ruins of the two principal temples: the Temple of Hera (6th century BCE) and the Temple of Zeus (5th century BCE) still remain.  Throughout Antiquity this Temple was considered the most perfect example of the Doric order.  This sanctuary also contained one of the highest concentrations of masterpieces of the ancient Mediterranean world though many have since been lost.  In connection with the cult of Zeus the Altis was then given the name Olympia, with famous Olympia, Greece being built on this site where also the first Olympic Games took place here, once every four years.

Supporting paragraphs: Nemean lion Heracles
Answer: Zeus and Alcmene