My dad recently committed suicide, I'll be 24 next month, him and my mother separated in 2018, they were fixing to get a divorce, my dad had a girlfriend and ended up having another baby, who is now a year old. I went to get a few tools out of our building after his passing (I live in an apartment but this is my child hood home) later that day I was asked if my fiance had went in and got some tools and we was told to bring everything back and to ask next time before we took anything. This is his girlfriend who he's been with almost 2 years... also was told by her and my dad's sisters that the home was in foreclosure... this has been so horrible for me, so much bad happened in such little time.. am I in the wrong for wanting my aunts (&uncle) to shove it and make her leave my dad's home...my mother found out that the home was still In her and my dads name & that it's been paid off since 2017.. this woman and my dad arguing is what has caused my dad to not be here with us and it's killing my soul... I need advice, my family has lied to my face, and really built this lie up... I can't hardly believe all this is real..
You "have been told" isn't good enough. You need to check on this legally. Get a lawyer to help you check if the house is in foreclosure. If there is a will leaving everything to the girlfriend then it is likely to be hers, but if there is no will then the wife and children inherit according to the dictates of the laws of your state. This is clearly something you need to have legal knowledge of because this home and ALL the property may belong to the wife who was not divorced and to his children, whether children of the marriage or otherwise. The girlfriend may have a claim for her child if DNA evidence shows this to be your Dad's child.
But long and short is that you need legal advice, not the opinion of those of us on forum who haven't a clue how all this was left. So sorry for your loss and all you are going through.
If the GF hadn't had a baby, then this would be just an affair partner of your dad. But with the 1-year-old, there could be issues involving what child support needs to be paid out of the estate.
I would encourage you strongly to see a will and estate lawyer. For sure, she is.
If not, and if there is no will, then you are on equal footing with his other biological child who's a year old. Just like with divorces, the courts tend to side with the best interests of an actual minor as opposed to a child who has attained majority.
If your Mom owns 1/2 the house, she should be able to check on any foreclosers. I really think since Mom still owns the house and still married to Dad she is the one who needs to deal with Dads death. Your Dads siblings have no rights her neither does his GF. You Mom holds the cards and you as his child. Unless, one of his siblings or the GF has been made Executor. Even so, they must do what the Will says. You and Mom should consult with a lawyer.