The introduction of the parenting theme is crass in the show, not least cos its way more interesting IRL Mitford.
Nancy - couldn't have any after an ectopic, sad for life.
Diana - two sets of DC, both removed by law. She pushed to be put into gaol 10 days after giving birth, knowing she'd lose the latest baby. Authorities pushed back, wanting to keep them together. Diana won and the baby and his Dbro were removed to foster care.
Pam - fostered some of Diana's children briefly and badly. No kids from 4 marriages, then lesbian.
Decca - first DC died of measles; second DC run over outside their house aged 8; 3rd DC died by suicide when living with them. The Donk, and I think another son, survived.
Debo - poor woman had at least 7 children, all died at birth bar 2.
Unity - failed to shag Hitler as planned, died with brain damage, no DC.
Nancy Mitford loathed her DM, who she cast in the books as vague Aunt Sadie, the hilariously vacant mother. Decca didn't like her either.
Lady R fought back with vigour at 'this awful insane portrait' - when the DD were grown, she spent forever visiting Diana at the abortion clinic and then gave up her life to look after Unity.
But you can't help feeling Nancy may have had a point in there somewhere.