Everyone here has a write-up, drawn from the same records that explain the names while you read the text.
Saul
King of Israel, before the splitIsrael's first king, given when the people demanded one 'like the nations.' Tall and promising, Saul started well but unraveled, offering an unlawful sacrifice, sparing what God had devoted to destruction, and hunting David out of jealousy. Rejected by God through Samuel, he ended by consulting a medium and falling on his own sword at Gilboa.
1 Samuel 9-101 Samuel 151 Samuel 31Study → David
King of Israel, before the splitThe shepherd-poet who killed Goliath, outlasted Saul's jealousy, and united the tribes with Jerusalem as his capital. A man after God's own heart, yet his adultery with Bathsheba and its cover-up cost him dearly. God promised his throne would endure forever, the covenant the Messiah would fulfill.
1 Samuel 16-172 Samuel 5-72 Samuel 11-12Study → Jonathan
Prince of IsraelSaul's son and heir, and David's closest friend, who protected the man who would take his own throne. He died with his father and brothers at Gilboa, and David's lament for him is one of the great elegies in Scripture.
1 Samuel 141 Samuel 18-202 Samuel 1:17-27
Bathsheba
Wife of David, mother of SolomonThe woman David saw from his roof, in an episode the text presents as the king's sin rather than hers, and whose husband Uriah he had killed to cover it. She later secured Solomon's succession, and Matthew lists her in the genealogy of Jesus.
2 Samuel 11-121 Kings 1Matthew 1:6
Nathan
Prophet in David's courtThe prophet who brought David both the covenant promise of an everlasting throne and, later, the parable of the poor man's lamb that trapped the king into condemning himself.
2 Samuel 72 Samuel 12:1-151 Kings 1
Gad
David's seerCalled David's seer, he advised him during the years on the run and later brought him the three-fold choice of judgment after the census.
1 Samuel 22:52 Samuel 24:11-14
Abner
Commander of Saul's armySaul's cousin and general, who kept the house of Saul on a throne for years after Gilboa, then quarreled with his puppet king and offered to hand the kingdom to David. Joab murdered him at the gate of Hebron, and David made a public point of grieving.
2 Samuel 2-3
Joab
David's commanderRuthless, effective, and impossible to control. He murdered rivals, killed Absalom against direct orders, and spoke to David more bluntly than anyone else dared, including telling him he was destroying his own army with his grief. David never managed to be rid of him and left the problem to Solomon.
2 Samuel 3:22-302 Samuel 18-191 Kings 2:5-6
Absalom
David's sonHandsome, aggrieved, and patient. After his sister Tamar was raped by their half-brother he waited two years and had the man killed, then spent four more years standing at the gate telling everyone their case would win if only he were judge. His revolt drove his father out of Jerusalem, and it ended with his hair caught in an oak and Joab's spears.
2 Samuel 13-18
Mephibosheth
Jonathan's sonDropped by his nurse as a child when the news came from Gilboa, and lame in both feet after. David hunted for anyone left of Saul's house in order to show kindness, and gave him his grandfather's land and a permanent place at the king's table.
2 Samuel 4:42 Samuel 9
Uriah
The HittiteOne of David's elite soldiers, a foreigner by descent, who would not sleep in his own house while the army was in the field. His refusal, the most honorable act in the chapter, is what forced David to have him killed, and he carried the letter that arranged it.
2 Samuel 11
Rizpah
Who guarded the bodiesAfter seven of Saul's descendants were executed and left exposed, she spread sackcloth on a rock and stayed from harvest until the rains, driving off birds by day and animals by night. When David heard, he gathered the bones and buried them properly.
2 Samuel 21:8-14
Tamar
Two women of this nameJudah's widowed daughter-in-law, denied the marriage the law owed her, who disguised herself and secured a child from Judah himself. He admits she was more righteous than he was. She stands in the genealogy of Jesus. A second Tamar, David's daughter, is raped by her half-brother Amnon.
Genesis 38:6-302 Samuel 13:1-22Matthew 1:3
Jashobeam
David's mighty menThe Thirty and the Three, listed at the close of 2 Samuel and again in 1 Chronicles: the men who fought with David through the wilderness years and afterward. Most appear only here, identified by their home town, which is why the lists are thick with words like Netophathite and Hushathite.
2 Samuel 23:8-391 Chronicles 11:10-471 Chronicles 12:1-40
Barzillai
The court and its servantsThe stewards, counselors, recorders, bodyguards, and hangers-on who fill the books of Samuel and Kings. Barzillai the Gileadite fed David's army in exile and then refused to come to the palace because at eighty he could no longer taste what he ate.
2 Samuel 15:19-222 Samuel 16:1-42 Samuel 17:5-16
Kish
Saul's familySaul's father, of Benjamin, whose lost donkeys sent his son on the errand that ended with Samuel anointing him king. Abner, Saul's cousin and army commander, held the northern kingdom together for two years after Saul's death before being murdered by Joab.
1 Samuel 9:1-102 Samuel 2:8-92 Samuel 3:26-27
Zeruiah
David's sister and her sonsDavid's sister, named far more often than her husband, and mother of Joab, Abishai, and Asahel. The three of them are David's hardest soldiers and his recurring problem.
2 Samuel 2:18-232 Samuel 3:392 Samuel 16:9-11
Amnon
Sons of DavidTwo of David's older sons, both of whom came to ruin. Amnon raped his half-sister Tamar and was killed two years later by her brother Absalom. Adonijah declared himself king while David was dying, was spared by Solomon, and was executed after asking for David's nurse as a wife.
2 Samuel 13:1-291 Kings 1:5-531 Kings 2:13-25
Ahithophel
The counselor who turnedDavid's advisor, whose counsel was regarded as if a man had inquired of the word of God, and who went over to Absalom's revolt. When his advice to strike immediately was set aside for worse advice, he went home, set his house in order, and hanged himself.
2 Samuel 15:12-312 Samuel 16:20-17:23Psalm 41:9
Amasa
The commander Joab killedDavid's nephew, made commander of Absalom's rebel army and then, after the revolt collapsed, offered Joab's job as a gesture of reconciliation. Joab took his beard as if to kiss him and stabbed him with a sword held in the other hand.
2 Samuel 17:252 Samuel 19:132 Samuel 20:8-12
Benaiah
Captain of the guardOne of David's mighty men, remembered for killing two Moabite champions, striking down a huge Egyptian with the man's own spear, and going down into a pit on a snowy day to kill a lion. Commanded the royal bodyguard, stayed loyal at Solomon's accession, and replaced Joab as commander of the army.
2 Samuel 23:20-231 Kings 1:38-401 Kings 2:29-35
Zadok
The two chief priestsDavid's two priests. Abiathar had escaped the massacre at Nob and joined David in the wilderness, carrying the ephod. Zadok's line came from Eleazar. At Solomon's accession Abiathar backed Adonijah and Zadok backed Solomon, and Abiathar was removed.
1 Samuel 22:20-232 Samuel 15:24-291 Kings 2:26-27
Ahimelech
Priest at NobThe priest who gave David the consecrated bread and Goliath's sword, not knowing he was a fugitive. Doeg the Edomite reported it, and Saul had eighty-five priests killed along with the whole town. Only Abiathar escaped.
1 Samuel 21:1-91 Samuel 22:9-232 Samuel 8:17
Hiram
King of TyreThe Phoenician king who supplied David and then Solomon with cedar, cypress, and skilled craftsmen for the palace and the temple, floating the timber down the coast in rafts. Paid in wheat and oil, and later given twenty Galilean towns he was not impressed by.
2 Samuel 5:111 Kings 5:1-121 Kings 9:10-14
Shimei
Who cursed DavidA Benjamite of Saul's house who walked along the ridge cursing David and throwing stones as he fled from Absalom. Abishai offered to remove his head; David said to let him curse, since the LORD might have told him to.
2 Samuel 16:5-132 Samuel 19:16-231 Kings 2:8-9
Machir
The clans of ManassehManasseh's son and the clan descended from him, who took Gilead east of the Jordan. In the Song of Deborah, Machir stands in for the whole tribe. A separate Machir of Lo-debar sheltered Mephibosheth and later supplied David during Absalom's revolt.
Genesis 50:23Numbers 32:39-41Deuteronomy 3:14
Maacah
Several of this nameA name borne by both men and women across the Old Testament. The best known is the queen mother, Abijah's wife and Asa's grandmother, whom Asa removed from her position because she had made an obscene image for Asherah. Another Maacah was the mother of Absalom, a foreign princess.
2 Samuel 3:31 Kings 15:132 Chronicles 15:16