A more thorough explanation:

Definition: A stranger in blood is someone who is not related by blood, such as a relative by marriage or adoption. It can also refer to any person who is not within the consideration of natural love and affection arising from a relationship.

• Your stepfather is a stranger in blood because he is not related to you by blood, but rather by marriage to your mother.
• An adopted child may be a stranger in blood to their adoptive parents, but they are still considered family.
• A friend or neighbor is a stranger in blood because they are not related to you by blood or marriage.

These examples illustrate how a person can be considered a stranger in blood even if they are considered family or close to you in some way. It is important to recognize that blood relation is not the only factor in determining familial relationships and that love and affection can arise from other types of relationships as well.