Your post still isn't clear (I'm not sure what "non lived with her" means) but I'm going to assume that your ex-wife and kids live with her Mom and brothers for most of the year.

You can't claim the children unless your ex-wife transfers the exemption to you using Form 8332.  For future years, that's something you may want the court to amend your child support agreement for.

Her parents or brothers may be able to claim the children in that situation if she is not required to file a return, of even if she is, if they have higher income than her.