OP, I'm sorry for your loss. Like others said, you should check out the laws. It's hard to believe that you and your brother have to pay off your father's debt. And even if has to be paid off, your mom needs to contribute from her share as well - it should be equally split 3 ways.
For my own effed up inheritance story: I had a cousin who died suddenly and left her only child(adult) daughter a couple mil in life insurance. She didn't give any instructions except to make sure her debts are paid off(which were low and easily covered) and to make sure her niece's college education was paid for.
You know this girl spent the whole lot on weed, spa trips, going to ATL to see where Real Housewives is taped, and refurbishing an old ghetto @ass house?
Now she has 3 kids and is on welfare and has some little business scams that she runs, and other flakey crap but didn't do a thing for the niece. The one
thing her mother asked for.