Based on the above facts, she does not file taxes. No he cannot. You could claim him if she signs form 8332, Release of Exemption. I assume grandparentes do not file either.
Disclaimer of California Attorney. Laws differ form state to state. Although the above response is believed to be accurate, it should not be relied upon as any type of legal advice because the information provided is incomplete. It is intended to educate the reader and a more definite answer should be based on a consultation with a lawyer. No attorney client relation is formed with me without a written contract.
Good Luck starts with a strategy and a plan.
Robert J. Suhajda, MS,CPA
17721 Norwalk Blvd. #43
Artesia, CA 90701
Tax Relief Lawyer. Former financial auditor and controller. Admitted to US Tax Court, Income Tax, IRS representation, Fiduciary income tax returns, Estate and Gift tax returns, Homeowner Association Strategist.
Since you have joint legal custody, your ex can sign a form 8332 releasing the deduction to you. It does not appear from your facts that your ex will have a filing requirement. Her boyfriend does not appear to meet the requirements to claim the deduction.
Any individual seeking legal advice for their own situation should retain their own legal counsel as this response provides information that is general in nature and not specific to any person's unique situation. Circular 230 Disclaimer - Advice given in this response cannot be used to eliminate penalties with the IRS or any other governmental agency.