In Greek mythology Demoptolemus was a suitor of Penelope who was killed by Odysseus.

Homer, Odyssey Book 22:

Meanwhile the suitors
were being stirred into action by Agelaus,
Damastor's son, by Eurynomus, Amphimedon,
Demoptolemus, Peisander, Polyctor's son,
and clever Polybus.

...

"Friends, now I'll give the word—let's hurl our spears  
into that crowd of suitors trying to kill us,
adding to the harmful acts they did before."

Once Odysseus spoke, they all took steady aim,
then threw their pointed spears.  Odysseus struck down
Demoptolemus, Telemachus hit Euryades,
the swineherd struck Elatus, and the cattle herder
killed Peisander. 

Characters in the Odyssey
House of Odysseus

Penelope (wife) Telemachus (son) Ctimene (sister) Anticlea (mother) Laërtes (father) Autolycus (grandfather) Eurycleia (chief servant) Mentor (advisor) Phemius (musician) Eumaeus (swineherd) Philoetius (cowherd) Melanthius (goatherd) Melantho (maid) Argos (pet-dog)

Monarchs and royals

Alcinous of Phaeacia Arete of Phaeacia Nestor of Pylos Menelaus of Sparta Helen Princess Nausicaa of Phaeacia Agamemnon of Mycenae

Gods

Aeolus (wind god) Athena Apollo Artemis Atlas Calypso Circe Helios Hermes Poseidon Zeus Oceanus Old Man of the Sea

Others

Achilles Ajax Amphimedon Anticlus Antiphates Antiphus Aretus Cyclopes Demodocus Demoptolemus Deucalion Dolius Echephron Echetus Elpenor Eupeithes Euryalus Eurylochus Halitherses Heracles Idomeneus Irus Kikonians Laodamas Laestrygones Medon Mentes Mesaulius Peisistratus Perimedes Perseus Polites Polydamna Polyphemus Scylla and Charybdis Sirens Stratichus Suitors of Penelope Tiresias Theoclymenus Thrasymedes

Suitors

Agelaus Amphinomus Antinous Ctesippus Eurymachus Leodes

References

Reece, Steve (1995). "The Three Circuits of the Suitors: A Ring Composition in Odyssey 17-22" (PDF). Oral Tradition. 10 (1): 207–229. Retrieved 2010-03-09.
Pope, Alexander (2008). The Odyssey of Homer. Wildside Press LLC. p. 344. ISBN 1-4344-6138-6.