Not sure what you mean by "multiple" trees, unless you're referring to the separate trees one can create on ancestry.com.
The wikitree concept is one-profile-per-person. So, rather than having separate lists for separate families, a single profile is created for each person, whatever their lineage, and the profile is shared by everyone here on wikitree.
That concept is based on the assumption that everyone is connected, perhaps generations and generations ago.