Both Uses

relative
in
A Living Nightmare - Cirque Du Freak book 1
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New visitors arrived, relatives of Steve's, and Mom decided to leave them alone with him and his mother.†
Chpt 23 *
"Speed is relative," he said, tugging his red cloak tight around his shoulders, pulling back into the shadows so we could not be seen, and that was all the answer he gave.†
Chpt 26 *

Definitions:

(1) (relative as in: the relative importance)
compared with something else (not an absolute value or not complete)
(2) (relative as in: they are relatives)
connected
in various senses, including:
- a person related by blood or marriage -- as in "The hospital won't let me visit her because I'm not a relative."
- a plant or animal related by origin or grouping -- "The closest relative of the dog is the gray wolf."
(3) (relative as in: questions relative to the topic)
related to
(4) (meaning too rare to warrant focus)
More specialized and less common senses of the word are found in philosophy, grammar, and music. Consult a comprehensive dictionary if you wish to see those. All senses have to do with relationships.