When they talk about it, it's crazy to think about how different their childhoods were. For Bolin, most of his childhood memories are of life on the streets. The memories he does have of life before the fire that claimed his parents lives aren't really so different from Jinora's, but those memories are vastly outnumbered by time spent living on the streets. For Jinora, her memories are mostly made up of all the things to do and places to go on Air Temple Island. Of Ikki and Meelo being annoying, and of reading to Rohan in the library.
For Jinora, childhood was a whirl of all the things it should be: learning to airbend, time spent with her family, reading books- the biggest danger in Jinora's life was that she would get in trouble for staying up to late reading. And she did it all with a full belly.
For Bolin, childhood was a whirlwind of all it should not be: fighting for his life, going hungry for days on end. Almost never any time to play, and certainly never being taught how to properly earthbend or read. His family consisted of Mako, and often times Mako would disappear for hours on end, trying to make enough money to get at least Bolin's belly full, and maybe have a scarp or two left over for himself.
They were raised in completely different worlds, and they lived completely different lives. The very elements they bend are opposites.
But Jinora has never seen an earthbender so light on their feet, and Bolin doesn't think there could ever have been an airbender as steady as Jinora.
So who cares if they had opposite childhoods?