Axl wrote Estranged by himself with his piano, then brought it to the rest of the band and Slash added the riffs and solos to it.
the song is Axl's 'baby'
ive heard Axl say somethin like he can relate the song to the divorce with Erin, break up with Stephanie also leadin to Axl loosin contact with Dylan (Steph's son) as Axl wanted to be a father figure to him, and also the situation with steven adler. Communication losted with family and friends too