Excess Taxes!!!!!!

My mother died, and had 3 children. I'm almost through settling her estate, and have already paid California Tax and Federal taxes amounting to over 300,000.00. After paying this, and dividing up the leftover into 3 persons, it seems we, as indviduals are being really gouged again.
My question is since we each have a third, and if we are not cashing it in, but leaving the money with Salomon Smith Barney, as it was originally with our Mom, why are we having to pay so much more in tax, individually, and will this be an every year thing?

>>why are we having to pay so much more in tax, individually, and will this be an every year thing?<<

You're not,...the Estate paid the taxes.
They are Estate Taxes, not income taxes.