Persistent of same reference twice


I tried to save an object - (object1) that is contained by 2 different objects (object2 and object3).
first, when i saved object2 - it succeeded and the object was saved (object 2 contains object1)
than, i tried to save object3 (that contains also object1 - the same reference) and it cause
transient object exception.
i also noticed that in the object2 - object1 has id
and in the object3- object1 doesn’t have id although object1 is the same reference in both of the objects.

what should i do?
how could i inform object3 that object1 inside of him is already saves and has id…?

Thank you for your message. Would you mind send me your project file (containing your class diagram and ERD), also your sample code for creating and saving those objects to have a look? Thanks in advance!

Best regards,
Rain Wong