"To come" is often used as a synonym for "to happen". For example, "In 1918 (there) came a great flu epidemic." ("flu" is the subject) "During the reign of King Albert came a great plague." ("plague" is the subject) "Come rain or shine, the postman will deliver the mail." The last one is particularly interesting, and relevant to our discussion. It uses subjunctive mood (since the rain "come", not "comes") and means the same as "Should rain or shine come, the postman will deliver the mail." "Should rain or shine happen, the postman will deliver the mail." We are, at last, in a good position to understand "come to think of it". Infinitives can act as nouns. That is one of the things they do best. Since "to think of it" acts as a noun, it can be used as a subject in the same way that "rain" does in the above example. "Come to think of it" is grammatically the same as "come rain" and actually means "Come to think of it" = "happen to think of it" = "Should 'to think of it' come" = "should 'to think of it' happen" = "should that thought come to us"

"Come to think of it" means 刚刚想起来， or 意识到. Some examples: 1. "I had not seen my roommate in a week, come to think of it." Meaning: I just realized I had not seen my roommate in a week. 2. "You know, she is getting married this summer, come to think of it." Meaning: You know, she is getting married soon, I just remembered.

Hi Song English. This is a good question! The way the writer uses 'Come to think of it', would sound strange to someone attempting to read it literally. 1) I agree with Adrian, but would say sentence 1 is grammatically 'acceptable', opposed to 'correct'. In current United States english, 'come to think of it' is used when someone draws a conclusion about a fact or set of facts. They realize something after thinking about it, or reflecting on what they know. You specifically asked what 'it' refers to. It refers to a CONCLUSION which is drawn from two implied facts. 1.1- He and her are distant relatives. 1.2- Because they are on an island, many other citizens are ALSO distant relatives. 1.2 is the 'it', or the 'conclusion' that is realized when the character/writer 'comes to think of it'. In the second part of your question 2a,2b,2c are all correct, and all acceptable in common English. Yes - 2a, 2b, 2c would all have the same meaning. I hope this helps!

1 The sentence is grammatically correct. 'Come to think of it' is a colloquial expression which means 'if you think about it'. It is the writer or speaker who is suggesting this. 'It' is the proposition that 'everyone else on the island was her distant relative'. 2. 2c is the simplest and best way to say this. 2a and 2b are also grammatically correct and have the same meaning. 2d, 2e and 2f are incorrect, as the conjunctions 'and' and 'but' are not correctly inserted in to the sentences. It would be possible to rewrite them using 'and' or 'but', but this is unnecessary as the meaning is already clear.