So here are some thoughts about how the two books use characters in the role of the "Mother", and especially how they contrast such characters belonging to different moral "sides" of the story.
ETA: to readers linked to this without warning : this post contains spoilers for the serie of book A Song of Ice and Fire by George RR Martin. I advice against reading it before you've read those books. I do strongly reccomand reading them, though, because they're some of the best fantasy out there.
In Harry Potter, Lily is the ideal standart by which to judge all mothers thanks to her sacrifice. As a character, we know little about her, but she was a brillant student (as Slughorn oft fawns), judged responsible enough to become Head Girl, apparently moral enough to call onto James when he was bullying Snape (unless such behaviour can only be blamed on flirtation *handpalm*), well liked by most everyone who knew her, and very pretty. As far as I'm concerned, Lily's the biggest (and only) Mary Sue of those books, but that's just my opinion.
As a mother, of course, it was Lily's sacrifice that defeated Voldemort, and her love that was strong enough to protect Harry until Voldemort's resurection. James' death, as we're told, was powerless because he didn't sacrifice anything - he would have died anyway according to JKR. Regardless the writer's own commentary, though, it's the Mother's love that is potent for protection.
There is something slightly disturbing to the fact of reducing Lily to this one virtue of supreme mortherly love. No matter how bright, skilled, opiniated as she might have been, her greatest and more distinguished act was dying for the sake of her son. Because of course, all mothers should be willing to die to protect their children, shouldn't they ? I've once read a very thought inducing fanfic bycruisedirector, Lily's Choice, which had Lily eventually back and letting Voldemort's kill Harry, escaping alive, because her death wouldn't protect Harry (as far as she knew) while alive she could go on fighting against Voldemort and eventually avenge herself.
I'm not going to say what a mother ought to do. Just an exemple of reasonment to challenge what we consider without a thought a proper motherly behaviour.
I don't have much to say about Molly Wealsey, the other character coded very strongly as a Mother in HP. However, she as well, is positionned as caring about her children primarly : her Boggart takes the form of seeing all her family killed. We have few reason to doubt she'd do anything to protect them, but so far this has played very little in the plot.
So what I'm interested in is seeing how Lily Potter - this undoubtly good and admirable mother - is contrasted with Narcissa Malfoy. Since the beginning of the book the Malfoys have been set on - if not the evil side - the side of Antagonism. Draco's played rival to Harry in various nasty way thought the books. Lucius was willing to get a 11 years old girl killed to get back against a political rival. And of course, they've been tied since the beginning to Voldemort.
However comes the beginning of HBP, and we're presented with a much more morally ambiguous scene when we see Narcissa doing all that she can to get protection for Draco.
There's no doubt in anybody's mind that what Narcissa is doing is "good". As a mother she ought to do anything she can to save her son. Through that mean, she reminds us of Lily, even thought she doesn't put herself in a position of fighting Voldemort. Indeed, the Vow she makes Snape swear ends up with Dumbledore's death more certainly than if she had done nothing. But the scene makes her somewhat sympathtic, and opens the door to the possibility of complexification of the Malfoys' morality.
I'll get back to that later, let's skip to ASOIAF.
In Martin's books, the mothers I'm interested in are Catelyn Stark and Cersei Lannister. Both characters are motivated in a great part by wanting to protect their children. This is true in greater part for Cat where Cersei's also motivated by thirst for power and resentment. However, like with Cat, most of Cersei's more important actions come out of her role as a mother.
Like Lily, Catelyn's strongest identity is that of a mother. We know she'd do anything to protect her children. Sadly for Catelyn, in the greyer and muddier world of Westeros, dying doesn't suffice to do so. She does manage to rescue Bran from a murder attempt, then runs down South to investigate on the instigator of the assassin (without success). Kidnapping Tyrion (believing he was responsible) heightens the crisis between Lannisters and Starks. Later one, she frees James Lannister to trade him -against Robb's order - against her daughters. Lastly she takes hostage then executes the Frey's innocent dimwit in a futile attempt to save Robb.
When last we see her, her grief and thirst for revenge have made her into a monster ready to judge and execute innocent people to avenge what she percieved as betrayal from Brienne.
Cersei is also wholly ruthless in her attempt to protect her children. Before the opening of GoT, she's had Robert's bastard children murdered repeatedly to prevent people from realizing Robert isn't her children's father. Later, when Ned; unwilling to see children killed, warn her, she orchestrate Robert's death, and gets Ned in jail. Throughout ACoK, ASoS and AFfC, a lot of her actions are desperate move to protect her children - and to keep power for herself. When we see her grieve for Joffrey's death, she's not all that different from Cat herself.
Of course despite Catelyn's occasionnal harshness to Jon, we hardly picture her getting him killed just to ensure Robb's safety. However both Catelyn and Cersei are put in a desperate situation, as mothers, that most of their attempts to protect their children come to naught. By the time Cat dies, she thinks most of her children dead or as good as. Cersei, we know, has been prophecied she will see all her children die before dying herself. Thus it's not difficult to see that, despite being on two very different sides of the war and morality, they are not altogether dissimilar.
I'd also like to compare Narcissa's scene in Spinner's End to Catelyn's scene with James at the end of A Clash of King.
In both scene, the "Mother" comes to a character with a morally ambiguous status, to require his help to save their children. Both scenes end up with the swearing on an Oath which sacrality is made important in the course of the story. In one case because it's magically enforced with the death of the person swearing it, and in another becaus Jaime comes to weight on that oath all his honour ending up sending Brienne on that ill-fated quest of her. Amusingly enough, both scene have another female character who serves as witness to the oath : Brienne by coming with Jaime to make sure the trade happens and bring back Catelyn's daughters; Bellatrix by being the magical Binder of the Unbreakable Vow. In both cases, as of the state of either serie, we ignore yet how ultimely successful either oath will be to protect Draco on one hand, and Sansa and Arya on the other hand. (If I liked puns, I'd say that's still hanging in balance)
The main dissimilarity in those scenes is the power balance. Snape in Spinner's End has most of the power, even as he plays a dangerous game that requires him to answer Bellatrix' questions. Jaimes, however, is the Stark's prisonner and threatened by a sword to make his vow.
However, one of the similarity I find most interesting in both scene, is that nominally Catelyn like Narcissa are betraying their Lord. Narcissa even talking about Draco's mission goes against the loyalty to Voldemort that her whole family is supposed to uphold, as Bellatrix and even Snape don't hesitate to tell her. Catelyn goes against Robb's order by freeing Jaime, a disloyalty all the more costy for Robb when the Karstark tragedy happens.
Narcissa by doing so appeals to a higher moral necessity, that of protecting her only son. And when she asks it of Snape, she does it by appealling to all his ties to her family : his friendship to Lucius, his being Draco's favourite teacher. Those personnal loyalties are unrelated to the position to Voldemort, unlike Bellatrix she doesn't appear to care whether Snape is loyal or not to Voldemort. She goes against Voldemort's order to even tell Snape, and what she requires of him is ultimely with the third Vow, directly in contradiction. However she doesn't either put herself in a position of opposing Voldemort.
Catelyn likewise considers saving her daughters' lives more important that whatever strategical adventage keeping Jaime prisonner gives Robb, this despite how much she scorns and hates Jaime Lannister.
(ETA: re-reading Spinner's End chapter, i was amused to find a line describing Narcissa in those terms : "She was so pale that she seemed to shine in the darkness, the long blonde hair streaming down her back gave her the look of a drowned person". Throughout ASOIAF, the "drowned" image is symbolicaly coding Catelyn, associated with the Tully heraldic animal of the trout, and foreshadowing her death after which she was thrown into the Riverrun river)
The universality of motherly instinct of protection makes it a useful tool to make an antagonistic character sympathetic, or at least understandable. It works in the reverse, at least with Martin, when such mother's love can become ruthless and dangerous to others. It's a moral imperative that transcends antagonist and protagonist's sides (or the closer to such thing that ASOIAF has).
Indidentaly, pushing such motherly protection too far is condemned in both books. By the use of Dumbledore calling Petunia Dursley abusive in her raising of Dudley in HP; and in ASOIAF, partially with Cersei's ill-concerved over-protection of Joffrey (pointed at for exemple by Tyrion during the battle at the end of ACOK), but more strongly with Lysa Arryn's treatment of Robert Arryn.
All right that's all. All thoughts and comments are welcomed.