Hello,
There is a way on how you can access that data without development with the help of actions. Here is what you can do:
Let's say that parent of parent type of entity is "Entity".
1. Create a global action that has 1 input with EntityReference type that points to "Entity" and one output of EntityReference type that points to "Entity".
2. Add the logic to your action that copies value from input to output.
3. Save an publish that action.
4. Inside your workflow call that new action and pass to input parent of parent - you can reach that lookup for sure.
5. After message is called you get an access to record of parent of parent with all of the fields.
