Family dynamics can also be very complicated.
A relative through marriage lost her partner to a sudden heart attack. He hadn't written a will. (Foolish, I know.)
She had one child. (Said child was privately educated, paid for by the relative's work.) She was a high earner, so her partner was a SAHD. (He'd taken early retirement.) They'd been together about 16 yrs by the time he died. The partner had two children who had been educated in the state system. They had left school by the time that the relative's child started at a private nursery.
Although the partner had a good pension, the relative had been generous with her money, paying for improvements to her MIL's house and making money available for the SC, etc: "Whenever [the ex] asked for something, we gave it to her."
To her consternation, the partner's wife went after half the house - which had been paid for in its entirety by the relative (and she literally had all the receipts).
More understandably, she also went after the partner's pension.
The partner had been paying his ex maintenance - she had never worked while they were married and didn't take up employment afterwards.
By the time he died, his two older children had family of her own.
In spite of being told that the house was solely in the relative's name, the ex insisted on going to court to put a claim on it. (As part of the divorce agreement, the ex had what had been the family home, fully paid off.)
My relative had a good relationship with her SC. Nevertheless, she was informed by them - with reference to the house - "We have to support our mother in this."
What I'm trying to say is that when the SC have largely been brought up in another household, you can't expect a SGP, SM and SC to have a close relationship and it might be shortsighted to be too generous.