There really isn't anything to stop you from creating an anonymous placeholder profile for living individuals who connect you to your ancestors, i.e. parents and grandparents. In fact, WikiTree clearly permits and guides users in the process of Anonymization of profiles of living nuclear relatives and the very recently deceased.
You can read the details here: https://www.wikitree.com/wiki/Help:Anonymization
How to Anonymize
1. Click the Edit tab on the profile.
2. Change first and middle name fields to an initial or Anonymous.
- Leave both last name fields intact.
3. Clear out all date and location fields.
4. Clear out all sensitive information from the biography. Replace it with a message like "Family members: This person's information has been intentionally removed for privacy. Do not add any information to this profile."
- Leave the family relationships intact.
You must leave the last name fields and family relationships intact. Doing otherwise would defeat the purpose of creating an anonymous placeholder.
Having these placeholders enable you to utilize some of the both fun and useful features of WikiTree's database, including the Relationship Finder and the Connection Finder, both of which show how you are connected (however distantly!) to other users.
https://www.wikitree.com/wiki/Special:Connection
https://www.wikitree.com/wiki/Special:Relationship