There is no estate tax on an estate below $1,000,000. so, unless the estate he left is over that amount you will not need to be concerned there. As to you and your siblings, there is inheritance tax so, for your side of this, there are no concerns about taxes.
The reason originally used to generate the estate tax was not to hurt normal people and/or their children but to redistribute wealth and prevent a small group from becoming excessively powerful. Personally I think this has been perverted a bit but I cannot change that.
Estate is a legal term referring to the assets and obligations left behind when someone passes away. Inheritance refers to the distribution of the assets, after debts, of that same person. The estate tax is levied on the assets less debts (net assets) of the deceased. There are no taxes levied on the distribution of those net assets (inheritance).
If all you father's net assets totaled $133,000 there will be no taxes to be paid and you can feel free to distribute the money. Since it was invested in a non retirement account it cannot include an IRA or any other form of retirement funds subject to taxes. You need not be worried there.