Watch is a synonym of Catch. Catch is related to Receive. Receive is related to Obtain. 
Grandfather is related to Relative. Relative is related to Aunt. Aunt is a different concept from Uncle. 
Watch <--Synonym--> Catch <--RelatedTo--> Receive <--RelatedTo--> Obtain 
Grandfather <--RelatedTo--> Relative <--RelatedTo--> Aunt <--DistinctFrom--> Uncle 