A child has no automatic entitlement to any share of their parent's estate. A parent has full disposing power over their own assets. Section 117 refers to a moral duty - it is not an absolute.
If a parent wants to leave all of their money to the Cats and Dogs home, they can. That won't be easily set aside if the offspring are grown, healthy and comfortably off.
As Bronte asked, there is no valid reason, my wife as have I, had looked after my dad for the last 20 years up to his death and assume his wish to leave the house to me was for this reason.