Geneally they have to be in your home 6 mos. or more to qualify.
If he was responsible for over 50% of the cost of the child, he can claim the child as a dependent. That would mean that no one else was entitled to claim the child, including the father and mother.
To claim a child as a dependent on your taxes, the child must have lived with you and you must have provided support for over 50% of the year. So the mother in this case can claim her grandson on her taxes if she supported the child for at least 183 days out of the year, regardless of whether or not the mother of the child owes back child support.
Only if he's included in the claim.
That depends on the purpose of the forms. If you have any doubts, before completing the form you should ask if it is appropriate for you to sign the form because you are a step-parent or explain your parental relationship to the person who is asking you to sign the form. Even if you have already signed the forms, if you have provided accurate information and not misrepresented your parental relationship, you should have nothing to be concerned about. However, if you claim to be something that you are not, such as the child's birth parent, when you are not, or claim an authority that you do not have, such as legal guardianship when you are not the child's legal guardian, then you may have a problem. The meaning of Mother, Father, Parent or Guardian can even change from form to form, depending on the situation and what is legally required in law. Usually, Mother, Father or Parent will mean the people who have the day to day care for the child, as these people will normally be the ones responsible for paying any bills and looking after the child after any medical procedure, so should be able to decide what is in the child's best interests and can give informed consent if the child cannot do so. However, in some circumstances a Legal Guardian is required to consent to treatment. Usually this will be a parent, though only the birth mother automatically is a child's Guardian in all cases. A father becomes a child's guardian because he is acknowledged by the child's mither as the father. If a child is adopted, guardianship is transferred to the adopted parents and the birth parents lose guardianship. In other situations guardianship depends on the local law, custom, and decisions of the Courts. Guardianship usually ends when a child becomes an adult. If you have any doubts about your legal situation you should consult a lawyer.
No
yes you can
If she's kept the claim current.
Yes. If the child lives with her and is under 18.
The length of time for someone to claim child support can vary depending on the jurisdiction. Generally, the custodial parent can claim child support until the child reaches the age of majority, which is typically 18 years old. Some jurisdictions may allow for an extension of child support if the child is pursuing higher education.
As far as a new claim? No, that ended when the child turned 18.
They can only do so if the child is a qualifying child or relative anyway...and they provided the support.
In what? As for taxes, the one who has the child 51% of the time claims the child. See link below for more help.