Aang was never technically an orphan. He was raised によって monks in the Southern Air Temple. It's part of the culture of the air nomads and it is part of their religion (which most resembles Buddhism). The nuns lived in the East and West Air Temples as the monks lived in the North and South, but that doesn't mean that the women/men have never came to the other temples.
Actually some of the air nations were mainly female and some were mainly male. I know this because when Aang met Appa for the first time a lady airbender gave him an 林檎, アップル to give to his bison. I don't know how the lady/guy airbender's were brought together または how they met and created a baby airbender not really sure on the politics of the airbenders または what they did. But the nations seemed to be separated somewhat によって sex.
Nothing has really been written about Aang's original family または parents. In ancient Tibetan culture it was customary and sometimes required that each family relinquish at least one child to a monastery; this would gain social merit for the family, and access to an education and religious fulfillment for the child. The child would have very little または no contact with his / her former family, thus the monks または nuns would become their family. Aang would have been sent to a monastery at a young age and all ties with his parents may have been severed, so any mention of this may not have been seen as something necessary to the story.
Aang had birth parents, but he was taken away at a young age to be raised によって the monks. I would like to know もっと見る about his birth parents though. The only time we see them is in shadow right after Aang was born in 'The アバター and the 火災, 火 Lord'.