My mother passed away this month and my concern is her 401K's they are from 5 different companies and there is issues with death benefits I do not understand as a beneficiary in the state of California.My mom wishes for her 6 grandchildren to get this money but only 2 of us are the beneficiaries that are suppose to handle giving out this money.

What I need to find out is if this is true that we are to be taxed federal and state from these 401K companies, do we then have to be taxed again when we do our taxes? Do we add this to our income come tax time?

Any withdrawal is treated as your income.
The 401K companies will withhold tax on the withdrawal amount.

You will file your tax return and report withdrawal as your income. You will also report the tax withheld by 401k companies as tax you have already paid. So you may get a refund or you may owe additional tax depending upon your total income.