Robert Chase was the diagnostic team's surgeon and intensive care (intensivist) specialist during the first three seasons.He has been on the diagnostic team with House longer than either of other two members at the time.
Near the end of the eighth season, he temporarily resigns, but returns after House fakes his own death and becomes the Head of Diagnostics, replacing House. Rowan had emigrated to Australia from Czechoslovakia a few years before Robert was born.
The name of Chase‘s mother has never been revealed.
It is presumed Robert has other siblings (most likely half or step-siblings), but their names have never been revealed.
However in "Better Half," he reveals that he has a younger sister who he took care of.
He also commented that she "ended up drinking half her life away and hating me," but he did call her at the end of the episode.
However, Chase had a rough relationship with both his absent father and alcoholic mother.
When Chase's father left the family, 15 year old Chase was forced to care for his mother until her death which is approximately ten years before Season 1.
Dealing with his mother helped him empathize with Luke Palmeiro, another teenager who was trying to deal with a parent who couldn't care for herself.
With what appears to be a total lack of parental supervision during his adolescence, Chase admits to having wild teenage years and experimented with drugs and sex.