What @timeisnotaline said.
Father who didn’t put his children first who were dependant on him will not put his grown up children first. Never.
OP, you’re flogging a dead horse. Your father made it clear that his wife comes first in the pecking order.
I’m shocked (not) that he paid measly £4.5 for his kids while holding a profession that pays very well. Absolute bastard thing to do.
Please cut your losses and put your family first- your DH, DC and PIL if they are decent. It’s difficult to understand why people behave this way and cut their children off but it’s their choice.
Sadly speaking from experience.My father called me years ago to say that he didn’t wish to stay in touch. I know it was instigated by his partner as she wanted him all to himself. He died last year and his family had to arrange the funeral.
We have similar situation with FIL and his wife- her family is put on pedestal while our is suppose to accept the crumbs. We said “no” to such shitty treatment and are NC now for a few years. It’s bliss,no dramas, demands and insults.
Good luck. Keep the good people in your life and don’t waste your emotional energy on arseholes, whether they’re related or not.