Although the tax result @TomD8 stated in the foregoing post may be technically correct in certain circumstances, they do not necessarily apply to the facts laid out in the original post.
Again, @mts658, you want to make the argument that the transfer via the quitclaim deed created, de facto, an implied (retained) life estate for your mother with the remainder to the siblings.
If your mother had a life estate, then the basis of the property in the hands of the siblings would be stepped up to its fair market value on the date of your mother's passing. This is a highly desirable result versus taking the property, in fee simple absolute, as a inter vivos gift at the time of the transfer.
A gift tax return should have been filed at the time of the transfer since the transfer included a future interest (the remainder to the siblings was a future interest). However, unless gift tax was owed (highly unlikely), there is no penalty for not doing so.
Again, refer to the link and Regulation in my previous post when you consult a tax professional and/or legal counsel.
