I am trying to find my deceased father's other children. My mother, who I haven't talked to in 10 years won't tell me anything. I have an estate paper from his death that has 2 girls listed on there. My father was 48 when he fathered me. I would assume these girls are much older. The last names of the girls are the same as mine and I would imagine they have gotten married. Does ayone have any suggestions on how I might find these sisters of mine? I did try Facebook, ancestory.com. But didn't find anything.

Put an ad in the paper local to where you think he lived when they were growing up.
Your best bet of course is to not be estranged from your mother.

Its not my choice to be estranged from her. Also I am not sure if the paper thing will work. There is such an age gap, they probably don't even know I exsist. Do you know of any good websites?

Nothing is going to be sure.
You have so little information that anything online is going to be almost useless.
Even better than an ad is to go there, and walk into post offices and shops and newspapers, and the library archives of papers.