Pair is a type of Unite. Pair is related to Sock. Sock is related to Ankle. 
Muscle is related to Strong. Strong is related to Bitter. Bitter is related to Chocolate. 
Unite <--IsA-- Pair <--RelatedTo--> Sock <--RelatedTo--> Ankle 
Muscle <--RelatedTo--> Strong <--RelatedTo--> Bitter <--RelatedTo--> Chocolate 