All 4 Uses of

relative
in
The Lightning Thief

I came from a relatively poor family.†
Chpt 16 *

relatively = in comparison to something else

Nothing like watching your relatives fight, I always say.†
Chpt 20 *

relatives = people related by blood or marriage

Grover panted, when we'd collapsed in the relative safety of a black poplar grove.†
Chpt 19

20 I BATTLE MY JERK RELATIVE A Coast Guard boat picked us up, but they were too busy to keep us for long, or to wonder how three kids in street clothes had gotten out into the middle of the bay.†
Chpt 20

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)
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.