A least one-third. If she needs more, she can petition for Year's Support on top of that. She should probably petition to be appointed administrator of his estate to get control of the process. When stepchildren are involved, it can get messy. She should consult with a local probate attorney and develop a plan of action.
Assuming that this is a case where the deceased husband had his primary residence in Georgia, then Mr. Schaeffer has given you a very good answer. I would like to clarify that the surviving spouse's share is based on the husband's probate estate - which is not necessarily the same thing as his assets. The surviving spouse would also be fully entitled to any assets which she and her late husband owned as joint tenants with rights of survivorship (typically, joint bank or brokerage accounts are default owned this way, while real estate must state "joint tenants," "with rights of survivorship" or some similar wording on the deed for any jointly owned real estate to be held as joint tenants), since that property does not become part of the probate estate. The surviving spouse is also fully entitled to any assets she receives as a designated beneficiary, such as assets from an IRA account, a life insurance policy, or a bank account with a "payable on death" designation where the spouse was designated as a beneficiary. The children would not be entitled to share in non-probate assets which pass to the surviving spouse. Similarly, if there are non-probate assets which pass to the children, the surviving spouse does not receive a share of those assets. The spouse needs to consult an experienced probate attorney as soon as possible, to help her figure out what rights she may have. The children may also want to do so.
This answer is not intended to provide you with specific legal advice regarding your situation, or to create any attorney-client relationship. The intent is only to provide general information. You should be aware that you cannot rely on this answer to provide you with any protection against tax penalties. You should always consult your own attorney in order to obtain legal advice.
1. She may be able to claim some (or all) of the estate by Years Support (if she acts in time).
2. She may get some property (possibly bank accounts, investments and homes) depending on how they are titled (was there a right of survivorship).
3. The percentage in an intestate division depends on how many children there were. Her minimum is 1/3.
She needs to get a lawyer ASAP. In many cases stepmom and children end up litigating their disagreements in court. Timing matters in these cases. Sometimes she who acts first (with counsel) has an advantage. This is a case where prompt retention of counsel may make a huge difference in the outcome.
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