You can find it on the pokewalker or just use the Safari Zone and walk in the tall grass in the Wasteland.
safari zone and rock tunnel.
go for a walk in your pokewalker (forest) and youll find some (hopefully) but they have low lvs at about lv. 8
great marsh
You can find some Kangaskhan in the Great Marsh, so be sure to look from the second floor of the Observation Deck of the Great Marsh to find areas where Kangaskhan can be found.
you find kangaskhan in area 2 of the safari zone in Pokemon leaf Green ... not sure in fire red sorry
You can find him/her in the safari zone.(If you beat the Elite Four.)
You can find it in the rock tunnel, but it is rather rare.
Kangaskan cannot evolve.
After the game, go to the Great Marsh and search.
you need to find it in the safari zone in area1.
Since it's a Kanto Pokemon, it must be traded from FR/LG.
The baby in a Kangaskhan's pouch is merely a younger Kangaskhan.