I don't think they are the Cazalet Chronicles (which I haven't read) but the description of those reminds me a little bit of the ones I'm looking for.
From what I remember it's an English family saga, not wealthy but solidly middle/upper (to my mind anyhow). The main character is possibly a woman, who fails at organising the house or has no interest in it, or is a DIL living with or close to MIL in the main house. Possibly her DH is not as wealthy as others, and she has possibly has no cook.
Family seem to come to visit the main house -married sons and their wives - I strongly remember a married couple who sleep with their window open because both think the other prefers that and neither will ask to shut it.
I realise that I'm not giving much to go on. It's probably been about 20 years since I read it (or them, I'm fairly sure there was a series).