Krishn's Parents
Krishn's father was Vasudev. He was a good friend of Kans (Krishn's Maamaa). Kans had a sister Devakee whom he loved very much so he married her to Vasudev to strengthen his relations with him. Krishn was the 8th son of Vasudev and Devakee.

Krishn's 6 Elder Brothers
According to the story in  Harivansh, Hiranyakashyap had another son, besides Prahlaad, called Kaalnemi. In fact Kaalnemi appears in different demon forms in each Yug and gets killed by Lord. In Tretaa Yug he was Raavan's uncle. This Kaalnemi of Dwaapar Yug had 6 sons (they were the son's of Maharshi Mareechi in their previous birth). They were born as Kaalnemi's children because of a curse from Sage Deval. They were called shad-garbhaa and their names were Hans, Suvikram, Krahta, Daman, Ripumardan and Krodh-hantaa.

These grandsons of Hiranyakashyp did not accept Hiranykashyap as their God and refused to chant "Hiranyaaya Namah" as instructed. Instead they did severe penance to please Brahmaa Jee. Brahmaa Jee was pleased and appeared before them and gave the boon they asked for. They asked he boon not to get killed by any Devtaa, or Gandharv, Yaksh or Naag. After receiving the boons, they stayed under water and enjoyed full freedom there.

Hiranyakshyap knew this and was very upset about their paying respect to Brahmaa Jee instead of him, so he cursed them that they would be killed by their own father in their next birth. Now, Kaalnemi took birth as King Ugrasen's son Kans. And these Shad-garbhaa (Shad means six) took birth from Devakee's womb as Krishn's elder brothers and as soon as they were born, all of them were killed by Kans. Kans was the incarnation of Kalanemi who was their father in their previous birth.

Seventh brother is Balaraam and the 8th one is Lord Himself as Krishn. Much later Krishn brought all his elder brothers killed by Kans and showed them to His mother Devakee. Bhaagavat Puraan does not mention Kaalnemi as Hiranykashyap's son. He is only mentioned as an Asur.

Krishn's Wives
Krishn had 16,008 wives. From among them 8 were the chief queens and other 16,000 were the women whom He released from Narakaasur's (Bhaumaasur) prison. Bhaagvat Puraan says that he had 10 sons from His each wife.

The celebrated eight wives of Krishn may refer to ----
--According to traditions, there are Asht Aishwarya - 8 states of supremacy - Animaa, Laghimaa, Mahimaa, Praapti, Praakaamya, Vashitwa, Ishitwa and Kaamaavashitaa.
--We may also note that the 58th chapter of the 10th canto of Bhaagvat Puraan is called Ashtam Ahishyudwaah.

(1) Rukminee
He first married Rukminee, the daughter of the King Bheeshmak. Rukminee was the part Avataar of Lakshmee. Bheeshmak wanted to marry Her to Shishupaal, but Rukminee wanted to marry Krishn, so when Bheeshmak was organizing Her Swayamvar, she sent a message of this matter to Krishn. Krishn rushed and kidnapped Her.

Her 10 sons are - (1) Pradyumna, (2) Chaarudeshn, (3) Sudeshn, (4) Chaarudeh, (5) Suchaaru, (6) Chaarugupt, (7) Bhadrachaaru, (8) Chaaruchandra, (9) Vichaaru and (10) Chaaru.
She had one daughter named Chaarumatee. Krishn married her to Kritavarmaa.

(2) Satyabhaamaa or Satyaa
Satyabhaamaa was the second wife of Krishn. She was the daughter of Satraajit (who blamed Krishn to steal Syaamantak Mani). She was born from the part of Bhoo Devee. After Satraajit blamed Krishn for stealing Syaamantak Mani, He searched for the Mani and brought it for him and handed over to him. Satraajit got so ashamed that he tried to give back that Mani to Krishn but Krishn did not accept it. Then he married his daughter Satyabhaamaa to Him.

Her 10 sons' names are - (1) Bhaanu, (2) Subhaanu, (3) Swarbhaanu, (4) Prabhaanu, (5) Bhaanumaan, (6) Chandrabhaanu, (7) Brihadbhaanu, (8) Atibhaanu, (9) Shreebhaanu and (10) Pratibhaanu.

(3) Kaalindee
Kaalindee was Krishn's third wife. She was the daughter of Soorya. He met her while she was doing Tap to marry Vishnu on the banks of Yamunaa River, so Krishn married her. Padm Puraan, 5/45 says that she was born from Leelaa Devee's part.

Her 10 sons were - (1) Shrut, (2) Kavi, (3) Vrish, (4) Veer, (5) Subaahu, (6) Bhadra, (7) Shaanti, (8) Darsh, (9) Poornamaas and the youngest one was (10) Somak.

(4) Mitravindaa
After Kaalindee Krishn married Mitravindaa. Mitravindaa was the daughter of Vasudev's sister Raajaadhidevee. She wanted to marry Krishn, so Krishn kidnapped her from her Swayamvar. [Padm Puraan, 5/45] says that Mitravindaa was the daughter of Vindaanuvind and He married her by tying 7 difficult bulls with one rope only.

Her 10 sons are - (1) Vrik, (2) Harsh, (3) Anila, (4) Gridhra, (5) Vardhaan, (6) Unnad, (7) Mahamsa, (8) Pavana, (9) Vahni and (10) Kshudhi.

(5) Jaambvatee
Jaambvatee was the daughter of Jaambvaan. This Jaambvaan was the same Jaambvaan who was with Raam. When Syaamantak Mani was lost and its blame went on Krishn that he had stolen it, He set off to find it to clear this blame. Krishn recovered the Syaamantak Mani from Jaambvaan's house. Jaambvaan married his daughter to Him, after a fight with Him for 27 days. It was when Krishn was looking for Syaamantak Mani and following the clues He came to the cave of Jaambvaan. After the fight, Jaambvaan recognized Him as his own Isht Dev Raam and gave Him Syaamantak Mani and married his daughter too to Him.
Padm Puraan, 5/45  says that Krishn fought with Jaambvaan only for 10 days.

Her 10 sons' names are - (1) Saamb, (2) Sumitra, (3) Purujit, (4) Shatajeet, (5) Sahastrajeet, (6) Vijaya, (7) Chitraketu, (8) Vasumaan, (9) Dravid and (10) Kratu.

(6) Naagnjitee
Naagnjitee was the daughter of the King Nagnjit, King of Ayodhyaa. Krishn married her by putting one rope in 7 difficult bulls' nose together.

Her 10 sons were - (1) Veer, (2) Chandra, (3) Ashwasen, (4) Chitragu, (5) Vegavaan, (6) Vrish, (7) Ama, (8) Shanku, (9) Vasu and (10) Kuntee. Amongst all of them, Kuntee was very powerful.

(7) Bhadraa
Bhadraa was the daughter of Vasudev's sister Shrutkeerti (married to the king of Kaikaya Desh).

Her 10 sons were - (1) Sangraamajeet, (2) Brihatsen, (3) Sur, (4) Praharan, (5) Arijeet, (6) Jaya, (7) Subhadra, (8) Vaam, (9) Aayur and (10) Satyak.

(8) Lakshmanaa
Lakshmanaa or Sulakshmanaa was the daughter of the King Brihatsen, King of Madra Desh. He married to her like Draupadee's condition - piercing the eye of a fish seeing its shadow in a pot filled with oil. Madra Desh's King had three daughters - Sulakshmanaa, Naagnjitee and Susheelaa. These three wanted to marry Krishn so they chose Krishn in their Swayamvar on the same day. Agni Puraan, 27 says that she was the Princess of Gaandhaar. Padm Puraan, 5/45 gives the name of Susheelaa instead of Bhadraa.

Her 10 sons were - (1) Praghosh, (2) Gaatravaan, (3) Sinha, (4) Bala, (5) Prabal, (6) Urdhwag, (7) Mahashakti, (8) Saha, (9) Oj and (10) Aparaajit.

All Puraan do not agree on the number of wives of Krishn. Bankim Chandra gives a list of 22 wives summing up all Puraan, Mahaabhaarat, and Harivansh. Then he deduces their number to 8 - by discarding 10 (which are only found in Harivansh), and 2 (who are only mentioned in Mausal Parv), and considering that Jaambvatee and Rohinee are the same, and Satyabhaamaa and Satyaa are also the same, that is, 22 - 10 - 2 - 2  = 8.

Bankim Chandra, in his "Krishn Charitra" says in the same chapter, in its last list
(1) Rukminee,
(2) Satyabhaamaa (alias Satyaa),
(3) Jaambavatee (alias rohini),
(4) Shaivyaa
(5) Kaalindee
(6) Mitravindaa
(7) Maadree
(8) Jalahaasinee Lakshmanaa

Another Set
(1) Rukminee,
(2) Satyabhaamaa - daughter of Satraajit
(3) Jaambavatee (alias Rohinee),
(4) Shaivyaa
(5) Kaalindee
(6) Mitravindaa
(7) Maadree
(8) Jalahaasinee Lakshmanaa
(9) Naagnjitee - daughter of Nagnjeet of Kosal - alias Satyaa

Vishnu Puraan, 4/11 gives Krishn's one of His 8 wives' name as Chaaruhaasinee and says that He had 180,000 sons from His 16,101 wives.

Krishn's Children
Apart from these 80 children from His 8 chief wives, he had many other children also.

Bhaagvat Puraan, 10/u9 says that "Since Krishn had more than 16,000 wives, so the number of His sons, grandsons, great-grandsons were in tens of millions."

Vishnu Puraan, 4/11 says that "Krishn's children and grandchildren etc cannot be counted even in hundred years. Because two Shlok are famous in this regard. Whoever Aachaarya (Guru) used to educate Yaadav princes, their number was 38.8 million, then how one can count those Yaadav who lived in the kingdom of king Ugrasen."

Krishn's Friends
Krishn had two fast friends - both were His childhood friends - Uddhav and Sudaamaa. Not much is found about Uddhav but one may read Sudaamaa's story here.