If the property was transferred before death, it's over. There isn't anything you can do about it so don't even think about it any more.
If they deeded the property to anyone during their lifetime it belongs to that person & won't be included in the probate, unless the property was part of a family trust, or some other arrangement.
If your surviving parent died intestate (without making a will) without leaving their home to you then their estate must be probated in order for title to the property to pass to the heirs. I am assuming your parents owned the property as joint tenants with the right of survivorship and after the first parent died their interest passed automatically to the surviving spouse. Intestate property passes according to the laws in the state where the property is located. You should collect and make copies of proof all mortage payments you made. You should also collect and make copies of all the property tax, insurance and repairs you have paid for. Your sibling is probably legally entitled to one half of the value of the property. Your lawyer should seek to charge off one half of every bill you have paid to maintain the property against your sibling's half in order to reduce the amount you will need to buy her interest and obtain clear title to the property. Perhaps the full amount of the mortgage payments could be deducted from your sibling's half. You should contact an attorney to discuss your rights, your options and how to arrange to have the title transferred to you legally.
You cannot acquire a Power of Attorney for a person who has died. If there is property that must be transferred, and no will, you must petition the probate court to be appointed the Administrator of your deceased sibling's estate.
The rights of adopted siblings in their sibling's intestate estate depend on state laws. In general, adopted siblings usually have the same inheritance rights as biological siblings if the adoption was completed before the sibling's death. It is important to consult with a legal professional familiar with the specific state's laws to understand the exact rights of adopted siblings in intestate succession.
Actually anyone can still come buy it, mother or father could still inherit it also.
There are none unless it's stated in a will, and or the senior sibling has power of attorney.
Both
Yes. No state can prevent you from leaving property to anyone, unless you or they have been convicted of certain crimes. However, the state of Florida does not recognize gay partners as legal families, so if you die intestate (without leaving a will), then all property will go to your next of kin, such as a child, sibling, parent, or cousin, and your partner will have no legal claim to any of it.
If the co-owner is agreeable or the house is titled in a way which allows the property to be transferred without the consent of other owners then it can be done using a quitclaim deed a simple and inexpensive procedure.
The sibling does not have the right to change a grant deed. Only the property owner can make such a change.
Generally yes, if your aunt died intestate with no living spouse, children or parents, you would be entitled to your deceased mother's intestate share of the estate. You should contact the attorney who is handling the estate.
The titling of the property detemines whether or not it is subject to probate procedure. No property can be sold, refinanced, distributed, transferred, etc. until it has been ruled exempt from inclusion into the estate of the deceased.