Its a known fact that Akbar adopted a few kids before he could have Salim. His most famous adopted son was Abdul Rahim Khan e Khana who was his second wife Salima Begum and Bairam Khans son. Main reason was before Salim quiet a few kids of Akbar died and may be he had lost all hope of having a kid of his own. In 16th century people had kid within 15-16 years old of age. Akbar did not have child till 27 years old. At 27-30 years people would become grandparents in those times. The average life span of a person was only 35 years that time. And for a king or emperor it was even more important to become a father and given an heir to throne and empire.
It is well documented in history that Nur Jahan and Jehangir did not have kids of own. So they adopted many girls who were orphan or poor and abandoned by their families and brought them up. In 16th century there were no orphanages as such. Some religious places would feed and take care of orphans. But otherwise there was no orphanage as such. If a baby or small kid was abandoned on streets it would die, become a slave of some rich mans house hold etc but there was no formal adotion as such. Some people would feel pity and give shelter to abandoned babies. In 21st century orphans are treated so badly even in orphanages so we can only imagne their situation in 15th or 16th century.
It is said Akbar too adopted a few kids especially a baby boy a few years before Salim was born. This was after his twins Hassan Hussein had died. People of empire indeed believed that Salim was born to Akbar because he adopted that boy child. The details of this adopted boy are not known to anyone. Akbar had this issue with detaling his family members detals in his official book Akbarnama. Even Salim is not mentioned from after he went to school till 30 plus years of age very rarely. Majority of his wives were never named in Akbar nama and only titles like Marium uz Zamani are given. So adopted kids being named and details being provided will be a distant dream.
Now everyone knows adoption was common in past for kings to get heirs. Raja Man Singh was adoped by Raja Bhagwan das of amer. Man Bai, Salims wife was born to her parents but had an adopted elder brother Man Singh. Raja Man Singh was just a few years younger to Akbar although Man Bai his sister was wife of Salim, Akbars son. So there was a huge age difference between when Raja Man Singh was adopted and Man Bai was born to her parents.
Salim too adopted a few kids who were abondoned. There is a story of once Salim going to war expedition as a young 10-12 year old. One day his Cheetah refused to come with entourage and ran behind a bush in an outskirts of a village and refused to come back when its trainer called it. Salim sent the trainer to get Cheetah back, but the trainer said there was something the Cheetah found in the bush and refusing to come out. The Cheetah had got a baby’s smell and was inspecting it. Finally a body gaurd of Salim went and got the baby who was just born and thrown in bushes by its parents. Salim took baby to his war camp and gave it to the servants to take care of it. Once it was stable and good health he sent it to Agra to bring it up. Akbar gave the baby to his senior wife for upbringing. Salim always took his pet cheetah’s, deers etc along with him with his entourage where ever he went even to war fields. So like this example rich people did adopt orphaned and babies thrown on roads and bushes but that was a rare thing. Because that time caste and religion was much more rigid and adoption was rare. Yes the babies left on road would be brought up but more as slaves and maids of the rich masters who found them. Or they ended up like a courtesean anarkali etc for pleasure of their masters who brought them up or sold them to others for entertainment.
This is story of one such adopted child of Akbar. One day Akbar went on empire tour. Salim was a small kid and insisted that he will accompany his father on tour. So Akbar obliged him and took him on the tour. They stayed in the governors or Nawabs palace. One evening Akbar dressed up as commoner and decided to go around the new city. Salim insisted he wanted to go out with his father, finally Akbar conceded and took him out. After going out in city both were returning to the palace when they saw a dog trying to pull roti from a kids hand. Akbar chased the dog away and tried to find the parents of child but could not. So he carried theinjured child to palace and tried to find the childs parents. But it was later discovered that the childs parents had died and their relatives had abandoned the child to its fate. So Akbar took the girl child back to agra and she grew up in Agra fort. So such instances were rare but not uncommon in rich house holds to adopt unofficially abandoned children and bring them up. Some even became like family and stayed all life with the families they were adopted in.