"when he did meet someone we would be introduced and they’d integrate into the family but it hasn’t worked out like that."
Did you and your Siblings do that, with every person ypu had an interest in?
This might shock you, but older people can have casual sex as well.
He might not count it as 'meeting someone'. He might think of it that he's met someone to meet up with.
You're all forcing him to declare what this relationship is, when they might just be going with the flow.
It's common for older people to not settle down. People who would never have casually hooked up in their younger years and it can be a shock to the family.
She's the first person he's been with after his wife. He might not have known how he'd feel, or how he does feel.
I'm Widowed, my youngest is 22. I'm thinking about starting dating. That doesn't mean that my children have to know.
Using the contact with the Grandchildren is out of order. Do you not value the relationship that the children have with your father?