C# is case sensitive; these two lines do not refer to the same variable:
int SaveInt;
saveInt = Form1.xx[0].P[0].V[0].X;
Fix that, and it'll compile.
It won't work - you'll get null reference errors because you haven't created any
father
instances in the array
xx
- but it'll compile.
You need to something like this as well:
for (int i = 0; i < 3; i++)
{
xx[i] = new father();
}