It is not $1. The sale to your wife and siblings for $1 each is effectively a gift of the property. If your wife's father retained a life estate in the property, then you wife's basis (as well as her siblings) is the value of the property at the time of his death. Was a life estate deed prepared and recorded? A life estate deed needs to clearly state that the property is being conveyed "to life tenant (your wife's father, for life, then to the "remainderman" (your wife and her siblings). If this wasn't done, then the basis in the property would be your wife's father's basis in the land as it was gifted, and not inherited. In this case there would be no step-up on basis.
You should probably consult with an estate planning attorney.
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