When my dad died in 2008, the cost basis (value of the house on the day of his death) was $326,000. I sold it for $115k recently (May 2012).

It was a major loss for a lot of reasons - the drop in price doesn't worry me.

Do the siblings have to pay an inheritance tax from the sale of the house? There's obviously no capital gains.

... Do the siblings have to pay an inheritance tax from the sale of the house? There's obviously no capital gains.

Generally, inheritance taxes (the federal estate tax anyway) would be payable by the estate (or trust in your case) when distributed. If the trust held title to the house until now, it is probable that the tax would be upon the basis at time of death. But $326,000 is below the exclusion amount anyway.

If you mean state inheritance tax, one would have to know which state it is.