Nobody Knows (2004)

This is yet another highly-considered film that takes a lot of watching and leaves the viewer devastated by the end.  A Japanese flick purportedly based on a similar story, it tells of a fairly feckless mother who takes a run-down flat with her eldest son (all of 12 years-old) not bothering to advise the landlord that she has three younger children who are then smuggled in (two of them in suitcases).  The kids all have different fathers and have never been allowed to attend school, but form a cohesive family unit and are all richly drawn personalities.  However, Mum is soon off in pursuit of her own happiness leaving the eldest to fend for himself and the others.  She returns periodically and even sends money occasionally, but as her disappearances lengthen and the money dries up, the kids face a hand-to-mouth existence in their increasingly dirty and unhealthy apartment since all of the services have been cut-off..  They do their best and even find some happiness in each other's company and with a shy schoolgirl who has befriended them, but one knows that some tragedy lurks just around the corner.  And it really, really hurts when it comes!