Contesting a Will where there is no relationship with parent

There's a mistaken belief that Wills can easily be challenged if a spouse, child or dependant are not satisfied with what they've been left. (That is, by filing a family provision application.)

It's not correct. Only persons with a valid legal basis for making a claim will succeed in challenging a Will (or negotiating a satisfactory out of court settlement). It has nothing to do with 'the principle' of the matter.

What is estrangement? How does it affect a challenge to a Will?

Some might find it surprising to hear that a child who has not had any relationship with a parent for extended periods (that is, they're 'estranged') can still be successful in challenging a Will. It depends on the reason for the estrangement (amongst many other things).