I realise that parents CAN be inadequate, only behaving through their personal life experiences.
I have forgiven mine at last, though it took me until I was over forty to understand the dynamics of my/our childhood.
my grandmother died when my dm was just 4.....grandmother's dm died when she was just 11.
g-g-grandmother died when she was also 11.i think that's right, basically 4 generations of daughters/mothers without love/guidance/support.
my dm was a single parent in 1940---so shameful then, no financial support.
then dm met my father, and the first child of the marriage was born, within financial emotional security.
then another 2 dsis were born, but there was only enough love to go round for my dm's first dd.
then I was born, but my dm loved my dsis so much that she resented me to her dying day.( I was lost and abandoned ending up homeless and in total poverty)
dm always explained I was the "black sheep" to my siblings, which they as children responded to, and treated me accordingly.
my dsis 2 years younger ,behaved ,as an adult ,as though I was the smell under her nose...I am now nc.... but my dm was the architect of this.
tragedy struck when first dd died unexpectedly when she was just 14, my dm never recovered and died tragically.
this left 4 siblings with the dysfunctional relationship with each other, that continues to this day.
so yes, parents behaviour totally influences siblings relationship in the future.
....well it did to us.