I followed your instructions, which were to add the EventRelated table twice and then attach the first (parent) event to the event id and then the second (child) event to the event id. However when I look at the Event table and select the "+" button, it does not show me the relationships for that record.
EventID has an RI enforced one-to-many with the first ID in the related table, which I've renamed to EventIDChild.
EventID has an RI enforced one-to-many with the second ID in the related table, which I've renamed to EventIDParent.
Both IDs in the EventRelated table are FKs. I cannot create a duplicate entry by adding a ParentID = 2 ChildID = 1 more than once ... as you'd expect.
However I can create a record where ParentID = 1 and the ChildID = 2. Which means that I don't understand how to force both entries, as you suggested. Nor did my attempt to understand "...lower ID in the first event ...", which I took to mean Field One is the child (lower), while field 2 is the higher, or parent.
I thought I had understood and followed your instructions ... would you continue to help me?
sample attached.