How can I relate two profile schemas using foreign Key

Scenario:

Schema 1: Person

    Base Class: XDM Individual Profile

    Primary Identity: PersonKey

Schema 2: Account

    Base Class: XDM Business Account

    Primary Identity: AccountKey

Schema 3: Lead

    Base Class: XDM Individual Profile

    Primary Identity: LeadKey

    Foreign Key 1: PersonKey (many to One) 

    Foreign Key 2: AccountKey (many to One)

When I create a segment, I can see the data qualified when the conditions are based on Lead+Account attributes, but nothing qualifies when Segment is created for the conditions based on Lead+Person attributes.
Is it possible to setup a relationship between two Profile schemas?

TIA!