I am not a historian but have recently been doing a deep dive on Alexander and the Diadochoi so I think I can answer this within the subreddit guidelines. My sources are generally Diodorus Siculus and Arrian. Will try to cite specific books when possible.

After the death of Alexander the Diadochoi started having a series of conflicts with each other that ultimately lead to the deaths of the rest of Alexander's family. Different factions among the Diadochi had different goals both for Alexander's family, the Empire as a whole, and their respective areas of influence. I will try to go family member by family member to give an overview.

Philip Arrhidaeus (Alexander's half-brother by Philip II and Philinna). Was older than Alexander and purportedly had some sort of mental disability.

Philip Arrihadeaus was older than Alexander and was purported to have had some type of mental disability (the sources differ on what exactly that meant at the time). He was never a serious contender for Philip II's throne. After Alexander's death a compromise of sorts was initially reached. Philip Arrihdeaus was named King unless Roxana should give birth to a son. While Philip was named King, Perdiccas (one of Alexander's generals) was named named regent due to Philip's disability. Philip was eventually killed when Olympias with the aid of the King of Epirus claimed the Macedonian throne in the name of her grandson Alexander IV. The Macedonians under Eurydice (wife of Philip Arrihadeaus) refused to fight the mother of Alexander. Philip and Eurydice were held captive by Olympias who ordered the death of Philip and then forced Eurydice to kill herself. (Diadorus Siculus The Library of History, Volume 19.)

Cleopatra. Sister of Alexander. Daughter of Philip II and Olympias.

While Perdiccas was the regent of Alexander's empire, Olympias (mother of Cleopatra and Alexander) offered Cleopatra in marriage to Perdiccas. Perdiccas accepted causing him to break a betrothal with Nicaea (daughter of Antipater the satrap of Macedon and father of Cassander). This marriage would strengthen Perdiccas' rule substantially and caused Antipater, Antigonus (satrap of a portion of southwestern Asia Minor), and Craterus (a powerful general of Alexanders) agreed to opposed Perdiccas. When Perdiccas died in Egypt (after being murdered by Seleucus and other officers) Cleopatra spent several years in type of house arrest with many of the Diadochoi fearing the prestige another would gain should they marry Cleopatra. Eventually, rumors reached Antigonus that Ptolmey was planning to marry Cleopatra so Antigonus ordered her death at Sardes.

Olympias. Mother of Alexander the Great. Wife of Philip II

The death of Philip and Eurydice along with other actions as ruler of Macedonia caused the Macedonians to turn on Olympias. (Siculus Volume 19). Eventually Cassander (son of Antipater) defeated Olympias in a siege at Pydna. Cassander purportedly made certain promises to Olympias prior to her surrender (none of which were upheld) (He took her into his custody. . Cassander was at this time married to Thessalonike (a half sister of Alexander the Great she was the daughter of Philip II and a woman named Nicesipolis) providing him a link to the Argead dynasty. Eventually Cassander ordered the murder of Olympias but the 200 soldiers he sent refused to due the dead being awed by Olympias. However, some relatives of the victims of Olympias reprisals during her rule of Macedon killed her. (Siculus Volume 19).

Alexander IV. Son of Alexander the Great and his Bactrian wife Roxana. Roxana was pregnant with Alexander IV at the time of Alexander the Great's death.

After Olympias' death, Cassander had one of his trusted men, Glaucius, take Roxana and Alexander prisoner. He spent many years under house arrest.During the various conflicts of the Diadochoi, Alexander IV eventually grew to reach the age of 14 which caused many Macedonians to feel that Cassander should drop his regency and give Alexander full rule. The remaining Diadochoi were at this time Cassander in Macedonia and Greece, Ptolmey in Egypt, Lysimachus in Thrace and parts of western Asia Minor, and Antigonus in the rest of Asia Minor and the East. As rumblings spread in Macedonia, Cassander ordered Glaucius to murder Alexander IV and Roxana. (Siculus Book 19). Diadorous claims that the rest of the Diadochoi were relieved by their deaths.

Heracles. Was purported to be the illegitimate son of Alexander the Great and Barsine a daughter of the Satrap of Phrygia.

It was and is unknown if Heracles truly was a son of Alexander. Polyperchon (a former regent of Macedon allied to Olympias) who at this time still retained some power in the Peloponnese used Heracles in an attempt to regain power but turned on the boy and murdered him per some sort of agreement with Cassander.

Again I am not a professional historian and am not sure if the sourcing is up to the (rightly) tight standards here. But I have recently been fascinated by this period and wanted to give it a shot. If it isn't up to standards I totally understand.