Sorry for posting in the wrong forum but it wouldnt let me post in the tax forum. If you have already gotten your taxes done can your mom have them done again, through a different person then you, and claim you, even though you have already claimed yourself? If the answer is no what is the legality and why?

my husband and his ex have been divorced for 11 years, and they have two children together. it is stated in their divorce decree that she claims one child and he claims the other. when my husband and i went to file our taxes this year they got rejected stated that someone had already claimed the minor child on their tax form. please help, she shouldn’t have the right to just decide to claim both children. right? thanks in advance…

My mother passed away and I am in the process of getting custody of my 14 year old sister. I am 20 years old and I don’t really know what i’m doing….
He told me not to claim her on my taxes because HE is going to claim her … but he doesn’t know that I already claimed her …
He gives me $100 a month and he receives $660 a month in ss for having my sister when SHE LIVES WITH ME!
He is trying to get every benefit he can for having her when he doesn’t. He gave her to me and she hasn’t lived with him for the past 5 years anyway.
WAS IT WRONG THAT I CLAIMED HER? CAN HE EVEN CLAIM HER?
He seems so SURE that he is going to get away with everything he’s doing that it makes me feel like it’s true…….
I just want this to be over and he makes me feel scared that even when we go to court he is going to win….
HE DOES NOT WANT MY SISTER AND HE FEELS THAT I SHOULD BE HAPPY WITH WHATEVER HE DECIDES TO GIVE ME!
I don’t know how to deal with this and I don’t know if i should be worried that he’ll win or not….
If it wasn’t for my fiance my sister and I would already be out on the street.