Radha was a fictitious character attached to Krishna as his lover, during 13th century CE.
Infact, there was no word Radha Krishna, until Jayadeva (1170 – 1245 CE) composed Gita Govindam in early 13th century.
Bhagavata Purana (Srimad Bhagavatam), the only authentic book on Lord Krishna, was last edited around 1800 BCE and it does not mention any person named Radha.
Krishna lived in Vrindavan for only 11 years and 6 months. During this period, he was adored as a kid by gopikas who were elder to him.
There was one married woman (Vrishabhanuja) who played with Krishna.
Her actual name is not mentioned anywhere, but as she was daughter of a cow-herd Vrishabhanu, she was termed Vrishabhanuja (daughter of Vrishabhanu).
When Krishna was 8 years old, he used to play flute and 17 years old Vrishabhanuja used to dance to his music.
Infact, stories were created as if this lady was paternal aunt of Krishna and their love was incest relationship.
Her character was made famous to the extent that people started believing that Krishna was an adult in Vrindavan, who loved a married woman but left her and went on to marry 8 other women later.
Temples in north India were built with Radha Krishna idols.
In cinema and Television, Krishna was shown romancing multiple gopikas simultaneously.
Radha’s story was extended till their seperation when Krishna left for Mathura to kill his uncle Kansa and never returned to Vrindavan.
Radha was said to have waited for a lifetime, expecting her lover to return.
Bhakti Movement originated during 8th century CE in south India (Tamil Nadu and Kerala), and spread northwards. It swept over east and north India from the 15th century onwards, reaching its zenith between the 15th and 17th century CE.
Within this, Vaishnavism was promoted a lot with publicity given more to Bhagavad Gita and Krishna.
To make Krishna appear as paramatma (super soul), people created a fictitious world called ‘Goloka‘ and made Radha as Krishna’s companion in it.
Bhagavatam clearly mentions that Krishna is avatar of Lord Vishnu and when he came down to earth, everyone in VaikunTam also came to earth to accompany him.
Goddess Lakshmi incarnated as Rukmini.
Women who adored Rama during Ramayana era but could not marry him, became his other wives.
Rishis who wanted to remain in the company of Rama during Aranya Kanda in Dandakaranya, reincarnated as gopikas at Vrindavan.
Infact, the number 16000 gopikas is not real.
There are 72,000 nadis (nerve channels) of which around 16,000 are the most importan. Krishna is considered the first purna avatar, the mortal incarnation with full divine powers. Krishna is said to have mastered all the seven chakras and had the power to manifest anything he wanted out of thin air. It is possible to do so only when you have power of the 5 elements which is possible only when you open up all the chakras.
When you do so, all you nadis are in your own control. So when they say he had 16,000 wives, it just means that he had control over 16,000 nadis of his.
The acts and plans of God are meant to be Gopaneeya (secrets, not to be disclosed to everyone) and whoever keeps or understand this secret are Gopis and Gopikas (who came down to earth along with Vishnu to serve him during his incarnation as Krishna).
Lakshmi’s 8 forms (Ashta Lakshmi) have taken birth as 8 princess, who were officially married to Krishna.
Infact, none of his 8 marriages happened out of his wish or choice.
Rukmini sent a letter to Krishna expressing her love and asked him to save her from a forced marriage to Sisupala.
Satyabhama and Jambavati were gifted as wives by their respective fathers during Samantakamani episode.
Kalindi performed austerities to gain Krishna as husband.
Naagnajiti and Mitravinda chose Krishna in their respective swayamvaras. Krishna had to fight with brothers of Mitra Vinda after she declared her choice.
Lakshana had to be abducted from Swayamvara to save her.
Bhadra was offered by her brothers to Krishna.
How can a boy under 10 years have love or incest relationship with teenage or elder women ?
All gopis were attracted to Krishna, just like women adore a cute kid in the neighbourhood.
Only those who have not read Bhagavatam properly can create a love affair between kid and women.
Within the tenth chapter of the Bhagavatam, one of the gopis who Krishna plays with during his upbringing as a young boy is mentioned.
There were many gopis, but it is mentioned that by service of one particular gopi, Krishna is more pleased, and she is Vrishabhanuja.
Her devotion was mentioned as anaaradhyatE aaradhyatE, which means her worship methods were not like regular and routine ways.
From that line, Radha was derived by later generations.
In later centuries, Brahma Vaivarta Purana was edited to add a character named Radha and her curse story of Sridama.
This is where physical relation between Krishna and Radha was embedded and a story was created.
Radha was jealous of Krishna being with other gopi named Viraja. When she approaches to catch them red-handed, Krishna’s servant Sridama stopped her at entrance.
Radha cursed him to be born as in demon species.
In turn, Sridama curses Radha to be born in human form and get seperated from Krishna for 100 years.
Only after 100 years, she can meet Krishna back in goloka.
This story is fake and embedded, which can be confirmed from the fact that, Krishna left Vrindavan at the age of 11 years and 6 months to Mathura and never returned.
In Mathura, he lived for 10 years 6 months.
At the age of 22 years, he left for Dwaraka and settled there. He lived in Dwaraka for 105 years 3 months and never returned to Vrindavan in his lifetime.
So, after leaving Vrindavan and killing Kamsa on 14 December 3218 BCE (Siva Ratri), Krishna lived for another 116 years and 2 months.
Fake stories were created even to the extent to make believe that Radha was not born out of womb, but is a goddess beyond Lakshmi.
One such story tells that one day when Vrishabhanu and his wife Kirtida devi or Ratnagarbha devi were returning from Yamuna river after a bath, they saw something glowing across a pond which left him awestruck. It was a huge golden lotus. Getting attracted to size and colour of the lotus Vrishabhanu moved into the pond and noticed a baby girl in the middle of the flower, smiling and shining brighter than sun.
This fake Radha stories became popular in Bengal and Odisha (as Jayadeva lived in those areas) and later spread to entire north India.
In south India, most of the ancient Krishna temples still have idol of Krishna alone, or Krishna with Rukmini and or Satyabhama.
There is no ancient Radha Krishna temple in entire India or world. All such temples were built in past 700 years.