WikiTree can and does include living people, within the context of protecting their privacy.
Generally, official records such as birth certificates, marriages, death, census and so forth are released well after a person's death, although you can use personal knowledge, I would suggest exercising judgment as well.
Privacy legislation varies in different jurisdictions, and generally involves a requirement for informed consent. WikiTree has recently adopted the European standard referred to as GDPR.
Here is discussion thread that may be useful: https://www.wikitree.com/g2g/601685/significant-privacy-related-changes-to-wikitree-for-gdpr?show=601685#q601685
And an FAQ is published here: https://www.wikitree.com/wiki/Help:GDPR_FAQ