Relation Property: allow multiple Entries (or give us a new kind of "Multi-Select Relation"

In the "People" Collection we are able to add Properties, for example "Husband", "Wife" and so on.
But what about "Children"?

A person can have multiple children.
No one wants to add as many Properties to the profile as Genghis Khan has childs ...

One single Property should be able to store the links to multiple childs.