My deceased mother wanted to leave me and my siblings money from her 401k. She was married when she passed, but her husband was incarcerated. Does he lose all rights to the 401k?

No, he would still be her heir if they are still married.

But a 401K normally does not go to the estate, if they put a beneficiary on the plan, just like a life insurance policy, they included instructions on who were to get the money at their death with the 401K management company. So merely contact them and ask who the beneficiary is.

Hopefully she make those changes to what she wanted to happen. Sadly too many people want things to happen, but never do what is required to make it happen

Just because he is in jail doesn't mean he can't be named in a will and left money.
Who is named in the will, you and siblings and your deceased mother's husband? You don't say who is named, just what your mothers wishes were.

Tick

My husband passed away in Nov. I am trying to get new beneficiaries on the IRA's and all that I got from him. When filling them out I want our son and my deceased daughter's daughter(granddaughter) to receive the money.Our son will be the one to pay all bills for me. Do I put a lesser % in our son's portion so he will have it to pay any outstanding bills?