Mother is 86 years old. Can she leave a life estate to me in her will with the remaining brothers and sisters to inherit the estate after my death?

Yes. That is exactly how a life estate works. In her will, your mother could grant a life estate to you with the remainder to your siblings after your death. You would not have any ownership rights in the property and thus couldn't sell it, nor would you own any interest that could pass by a will. Upon your death the life estate would be extinguished and your siblings would own the property free and clear of your life estate.

By that arrangement you would have the right to the use and possession of the property for the duration of your natural life. You would be responsible for paying the taxes and maintenance costs and you must not cause any waste or damage to the property.

You should consult with an attorney who specializes in probate law ASAP. She/he can draft a proper will for your mother that meets the legal requirements for your jurisdiction and explain the options and consequences.