Needing A Dickensian Clue - Little Dorrit

[akirlu]

I've never read the original Dickens, but we just finished watching the 2008 production of Little Dorrit last night and I am confused. Are Amy Dorrit and Arthur Clennam half siblings born of different mothers, or not? The implication seems to be that Clennam pere may have been father to both, sired on two different ill-fated opera dancers, but it isn't at all clear. None of the synopses of Dickens that I've been able to dig up so far are clear on the point either, and one of them makes it seem that perhaps both are children of the same mother, Mr. Clennam's first wife who wrote so his uncle so touchingly that he changed his own will in favor of her and her get. Either way, it seems Arthur and Amy may be at least half-brother and -sister. Ending on an incestuous marriage seems a bit racy for the late 19th century, and also for Masterpiece Theater Classics, though. Hence my confusion. Anybody well-read in Dickens who can clear this up for me?