How do the definitions of "first-degree relative" and "nuclear family" differ?
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### Instruction:
How do the definitions of "first-degree relative" and "nuclear family" differ?

### Input:
A first-degree relative (FDR) is a person's parent (father or mother), full sibling (brother or sister) or child.[1] It constitutes a category of family members that largely overlaps with the term nuclear family, but without spouses.[2]

### Response:

A first-degree relative (FDR) is a person's parent (father or mother), full sibling (brother or sister) or child.[1] It constitutes a category of family members that largely overlaps with the term nuclear family, but without spouses.[2]
Nuclear family includes spouses while first-degree relatives are only blood related.