According to your introduction, the heirs include: stepmother, stepmother's son (because he is 16 years old and has not taken part in the work, he should be regarded as having formed a dependency relationship with Xiao Wang's father), Xiao Wang and other sisters.
Xiao Wang and other sisters are children of Xiao Wang's father. No matter whether you are an adult or not, no matter where your registered permanent residence is, the right of inheritance is equal.
Stepmother and father have no marriage certificate, so stepmother and stepson have no inheritance right, but if possible, they should be properly divided as the main support obligation to the decedent.
The renovation of old houses belongs to attachment. For the seized property, the party that obtains the ownership will provide compensation to the other party.
If the house belongs to the youngest son, I'm afraid you will have no property rights after many years. This problem is complicated, so it is recommended to consult a lawyer in detail.