Pant is related to Seat. Seat is related to Butt. 
Brother is related to Relative. Relative is the opposite of Absolute. Absolute is the opposite of Dependent. Dependent is the opposite of Independent. 
Pant <--RelatedTo--> Seat <--RelatedTo--> Butt 
Brother <--RelatedTo--> Relative <--Antonym--> Absolute <--Antonym--> Dependent <--Antonym--> Independent 