Event Error: Unknown relationship 'brother'

Expected Behavior

The event should proceed without error, instead it fails to initiate.

Current Behavior

Steps to Reproduce

1. Acquire a slave with a brother.
2. Wait for an event to trigger that involves slave's brother.
3. Event fails to initiate.

Additional information

• Release ID: version: 0.10.7.1, mod version: 4.0.0-alpha.7, build: 1134
• Commit: aff1a74d
• Save file Event_Error.save