Kangaskhan has the Ability Scrappy, But its Ability when it is Mega is Parental Bond.
Is Parental Bond added to Scrappy, or does it replace it?
When A Pokemon such as Kangaskan Mega Evolves Their old ability is replaced by a new one. The old ability is completely negated of all its effects and the new Ablity in this case Parental Bond is the new Ablity. If this was a thing it would be totally cool. Charizard Y with Solar Power and Drought at the same time would just be a dominating force. But I guess it would be confusing with Mega Rayquaza causing weather and yet making it go away...............
Mega Pokemon do not use the ability of their non mega form combined with their new ability. (If they have one.) So, Parental Bond replaces Scrappy.
Hope this helps!