You have asked an interesting question. There are different answers depending on the context in which the question is asked.
The scientific and legal meaning of descendant is all the persons who have descended from a common ancestor. In this context, a step-child would not be considered to be a descendant.
However, for purposes of inheritance, a legally adopted child and their issue are considered descendants. A step-child in a blended family who has not been legally adopted is not considered an heir at law.
To a genealogist who is researching a family line, an adopted child would be noted as adopted and not a descendant of the blood. Similarly, to a medical researcher who is examining a troublesome medical history, an adopted child in the family line would not be considered a descendant.
No, there must be a blood relationship.
You are considered the legal descendant, for purposes of inheritance, of the parent who is listed on your birth certificate. However, someone supplied false information at the time of the recording of the birth and that issue may come up in the future. A court order could change the situation but until that time the birth certificate would control.
No, there must be a blood relationship.
Lineal descent is metaphorically in a straight line; a lineal descendant is the child of the child of the child (repeat as necessary) of your own child. It is not the child of your sister, and so forth.
Yes. That is also what makes it legal for the step-parent to carry the step-child on their health insurance.
Not unless his mother is married to the man they are living with
A query regarding the identity of a descendant typically refers to a request for information about someone's lineage or ancestry, specifically inquiring about who their descendants are in their family tree. It seeks clarification on individuals who are directly related to a specific ancestor through a line of offspring.
Yes.
A male parent is considered to be the father of the child in most cases. A male parent can also be a step-father or even the grandfather of the child.
yes
yes he did, i am a descendant
If you are the child of your father and his first wife, then his second wife is your step-mother.
Maybe, but not normally. Unless the step-child was adopted they are not a descendant of the deceased. However, if their parent received the estate through their spouse, they may have a claim. You need to consult a probate attorney in your jurisdiction with all of the specifics.