Agamemnon was of Mycenae, and became the conqueror of Troy.
Cassandra was the daughter of Priam and Hecuba, thus a princess of Troy.
Cassandra was blessed with bad fortune. In her youth she had spent a night in the temple of Apollo where she was granted the gift of prophecy. Later, as an adult, she spent another night in the temple of Apollo, who found her attractive. She made the mistake of repulsing his advances. In his ire, Apollo cursed her with having all her prophecies disbelieved. Her father Priam eventually had her confined for a lunatic.
Agamemnon took Cassandra as a spoil of his Trojan conquest. She bore him twin sons named Teledamus and Penops.
Upon his return to Mycenae, both Agamemnon and his trophy were murdered by Agamemnon's wife Clytemnestra and her lover Aegisthus. Apparently Clytemnestra had no concept of poetic justice. Her lover Aegisthus, having not a lot to do, found time to murder the twins Teledamus and Penops.
Agamemnon had run afoul of Oeax. Odysseus wanted to sit out the Trojan War, and to effect that plan tried the insanity ploy, acting bug nutty enough to escape service in the war. Palamedes, (brother of Oeax), ratted out Odysseus, forcing him to go to war. Odysseus was not happy and framed Palamedes as a traitor. Agamemnon turned Palamedes over to the troops for punishment, where he was promptly stoned to death. So, long story short, Oeax put Clytemnestra up to the dirty deed to pay Agamemnon back for offing his brother. And to think they said Dallas had a lot of plot twists.
Poor Teledamus was but a peripheral character in this ancient soap opera. His role was that of victim, falling prey to the machinations of his elders.
Sources:
http://www.stanford.edu/~plomio/cassandra.html