Aunt claimed my kids on her taxes. kids were w/ me until may. She had temp. guardianship of only my son. Daughter never lived there. Also claimed my brother.wht do I do

Sounds like you have a messy/confusing situation.  We do not have enough details.  However, it does not sound like you had the children for more than half the year if you only had them until May.  We lack enough information about your daughter and brother to know if your aunt could claim them  or if you can claim them.   Provide some details.

An aunt, or even a  great aunt, is a close enough relative that she may claim your kids as her "qualifying child"  dependents, if they lived with her for more than half the year.  You can only claim your own children if they lived with you for more than half the year. 

That said, if someone else claimed your child inappropriately, and if they file first, your return will be rejected if e-filed. You would then need to file a return on paper, claiming the child as  appropriate. The IRS will process your return and send you your refund, in the normal time. Shortly (up to a year) thereafter, you'll receive a letter from the IRS, stating that your child was claimed on another return. It will tell you that if you made a mistake to file an amended return and if you didn't make a mistake to do nothing. The other party will get the same letter you did. If one of you doesn't file an amended return, unclaiming the child, the next letter, from the IRS, will require you to provide proof. Be sure to reply in a timely manner.

Winner gets the tax benefits; loser gets to pay the IRS back with penalties and interest.  The relative the children lived with the most usually wins. 

you can also use the iRS website to see if you qualify to claim any of your kids

https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent