If your mother died without leaving a will, you usually have a right to your mother's estate even if your siblings don't give want to you a share. Intestacy laws vary by state, but children of the deceased are usually the first in line to inherit, after a surviving spouse. Whoever files the petition for estate proceedings — your sibling, for example — has to notify you of the proceedings and must tell you about your mother's estate, including how much property she owned. You have the right to take part in your mother's estate proceedings. The person appointed by the court to oversee your mother's estate has to give you your share and file a release signed by you with the probate court. The release shows the court you received your share.
As is the case with estate proceedings without a will, you must be notified of probate proceedings on your mother's estate by whoever files a petition in court. Probate proceedings settle the estate of a person who died with a will. If your mother left you a share in her will, your siblings can't stop you from taking it unless the court finds the will isn't valid; the court follows state intestacy laws if the will isn't acceptable. The executor — a person appointed by the court to manage your mother's estate — must follow the will's directions. Once you receive your share, you'll have to sign a release for the executor.
If your mother left you out of the will or specifically disinherited you, you may contest the will by petitioning the probate court holding the estate proceedings. You must have a legal basis for contesting the will. Valid reasons to challenge a will vary by state but commonly focus on the person's state of mind or health when she made her will. If your mother wasn't in a sound state of mind when she made her will, for example, you can contest the will on that basis, but you must prove it. Medical records showing your mother had a disease that affected her mind, such as Alzheimer's, at the time the will was made and testimony from witnesses who knew her would help prove your case. Other reasons for contesting a will include undue influence — for example, your sibling pressured your mother into making the will — and forgery. If the judge rules the will isn't valid, you'll get a share of the estate according to the state's intestacy laws. However, if your mother's will had a "no-contest" clause — a term disinheriting a beneficiary who unsuccessfully challenges the will — you may get nothing if you lose.
Laws in some states, such as Washington, will provide you with a share of your mother's estate if the will didn't mention you at all and was made before you were born or adopted by her. If you believe your siblings are hiding your mother's assets, you can file a petition in the court handling your mother's estate to ask for an account. The executor or administrator of the estate has to provide you and the court with a line-item account of all your mother's assets and what he's done on the estate.