Caroline by Richmal Crompton (pub. 1936)

You've met Karen already, now meet her more dignified grand aunt who stays strictly within the private sphere. Caroline due to her supererogation and steely abnegation has created debts of gratitude which cannot be repaid except by utter fealty to her views. Those have the power of edicts and cover choice of spouse in the brother and sisters which she has reared. Full sister Marcia and half brother Robert and half sisters Susan and Fay were reared by her after:
(a) Mother Phillipa abandoned the family when she was eighteen. Divorced by Gordon who retains Caroline and Marcia
(b) Death of Stepmother
(c) Followed by Father Gordon's death two years later when the children were still young.

There are an aunt and an uncle on the Father's side who appear in the novel, Maggie and Charles. They play the parts of wally uncle and scatty aunt in this superb novel by a writer who is chiefly known for the William books. Caroline has the alien eye morphing death ray capacity which quells mutiny in the family and is a fine aid to discipline in the school where she teaches. She also translates, coaches and trains up servants to absolute efficiency. Her standards are very, very, very high and you will not meet them however you try.

Caroline laughed rather shortly.
“Auntie darling, you ask that question every time you come. I keep telling you. I simply hate a room cluttered up with furniture, and when I got that tallboy the obvious thing seemed to be to move the piano out.” Her eyes rested with pleasure on the mellow gleaming surface of the old walnut. “It’s a lovely thing, isn’t it? That corner’s been crying out for it for years. Pianos are such ugly articles of furniture. I love this room without it.”
“Fay played on it so nicely,” said Maggie. “Where is it now?”
“It’s stored,” said Caroline. “There wasn’t room for it in any other room.”
She’s irritated with Maggie for harping on the subject of the piano like that, thought Charles, watching her. It’s silly of Maggie, of course. She can’t remember things. She asked just the same questions the last time we were here. . . . Funny how Caroline’s eyes betrayed her exasperation rather than her voice or manner. They were almost grey when she was pleased, but they turned a clear cold blue when she was annoyed or irritated.

The real reason is that the last sibling left at home, Fay, is, in Caroline's view, being distracted from her studies for a scholarship by her love of music. The relentless and joyless pounding of her books is bringing on a nervous breakdown in the girl.

Robert and Susan are still living locally and both are married unsuitably, in Caroline's view, to Effie and Kenneth. She is working hard at disassembling those relationships and reordering them with tight lipped sweetness and light in a rational manner.

They went out together, Caroline’s arm still round Susan, Susan leaning against her like a disconsolate child. When Caroline returned, her brow was drawn into a frown.
“What’s the matter with Susan?” said Charles. “She’s a bit depressed, isn’t she?”
“I’m afraid that her marriage isn’t turning out very well,” said Caroline, closing the door behind her.
“Why?” said Richard. “He seems a decent chap.
“So nice-looking,” put in Maggie. “I like his curly hair.”
“I suppose he’s been spoilt,” said Caroline. “Only sons so often are, and”—she shrugged—“he’s been brought up in quite a different atmosphere from Susan, of course.”
“Don’t be a snob, Caroline,” said Richard.

Over in the establishment of Robert and Effie, Evelyn selected by Caroline runs the household. She is in charge of the children and the management of the house and servants bringing exemplary order and discipline to the chaos of ineffectual Effie.

Is this Strindberg in the Home Counties? No, there's a lot of humour and when you learn that Caroline has invited her mother that deserted them 18 years previously back to stay in the house one's narrative nous is alerted to the possibility of an agent who will break the emotional logjam. This sort of thing:

She moved her chair to make room for Fay to sit on the hearthrug at her feet, as she loved to do. She ought to tell the child about her mother. She must do it very carefully.
Fay rested her head against Caroline’s knees. She wanted to put off the moment of starting her home-work, but she felt that she couldn’t bear one of Caroline’s “little talks” just now.
“Sybil’s got the sweetest kitten,” she said, in order to start the conversation, at any rate, on a light note. “She’s called it Smoke.”
Caroline’s figure stiffened almost imperceptibly.
“Sybil?”
“Sybil Dickson. I called at her house with her on the way home.”
There was a short silence, then Caroline said:
“But, darling, I thought you’d come straight home from school.”
“I wasn’t there more than five minutes. I had to call anyway, because she’d got the copy of Heine. Fraulein had lent it to her and told her to hand it on to me afterwards.”
“I see. . . .”
A faint resentment stirred beneath the listlessness and depression of Fay’s spirit. Why did Caroline always make her feel that she’d done something wrong whenever she went home with any of the other girls or even waited for them after classes or games?

Ah Caroline, admired, the cynosure of every eye, to become whole you must taste defeat. Failure will be good for you. How is it to be wrought? Now read on.