This picture led to speculations that Brownberry might have been his mother ... and Rain his father. As far as I remember this discussion it was fan speculation without a clear hint for it.
In my opinion Rain is griefing about the death a tribe mate ... a loss that is made worse by the fact that he was too late to help.
And Brownberry ... perhaps she was simply the first one being there. Shale might have been a close friend, even a lovemate - or a cubling she helped to raise.
Anything is possible - but ... Does it really matter? The Wolfriders at that time were small enough in number and close enough in feeling and caring to be more like a family than a tribe.
Easter EggQuest 2014 found