Question

John,of whom my anut is a distant cousin by marriage ,comes

Answer 1

这个从句如果把它还原,是：

my aunt is a distant cousin of John（从句中用whom替代） by marriage

所以这个从句是一个系表结构作谓语,谓语是is a distant cousin of John,从句没有宾语,whom（替代John）是介词of的宾语

my aunt【主语】 is a distant cousin of John【系表结构作谓语】 by marriage【状语】