@makeadifferencey , in order to answer  your question , need to  have the following info:

(a) when did your father die -- is it 2019 or earlier

(b) did you get an appraisal of the inherited property  at the time and if so what was the  fair market value?

(c) was the house used for income generation ( rental ) from the time of death of the decedent and the sale to your sister ?

(d) what is the  "loss" of $75,000 ?

(e) the house is in the USA, right?

Hope to hear from you soon 

Yes, technically you have to report the sale, on your tax return; but you will not report any gain or loss.  You show 0 for your gain/loss. You have no gain because you sold it for less than your cost basis (the fair market value on the date of death of your step father).  

You cannot claim a loss because you sold it to a relative for less than market value. You essentially made a gift of equity to your sister and you may even  have to file a gift tax return, if the gift was worth more than $15,000.

For example, if your share was worth $50,000 at the time of the $26,000 sale, you gave her a $24,000 gift.  But, her cost basis is not $26,000 or even $50,000.  It’s what the property was worth when your stepfather died (unless that amount is less than $50,000).