Anthony Cooper is not Lockes father by Monika

John Locke was born in 1956.
Emily Locke was lets say 16 years old.
Her mother said: "He is twice your age"
Meaning he is around 30. Lets assume he is 32.
So Lockes father is born in 1924.
In 2004 he would be 80.
There is no way Anthony Cooper is 80 years old.

Anthony Cooper said to Sawyer that he was young when he was using the name Tom Sawyer. Young in July 1976 when he conned his parents.
If Anthony Cooper is Lockes father he had to be around 52. Is that young???

Unless Emily Locke was seeing two men at the same time. And I really don't see that happening. Anthony Cooper conned Locke. Conned him for his kidneys and conned him about being his daddy.

How he found the match? I have no idea. But kidneys can match even if you are not related to the doner. And since we know that events of the island were somehow influenced by certain people from the Island I wouldn't be surprise to see Jacob (I am sorry this happened to you) giving a tip to Cooper about Locke. Because the crucial thing in Lockes life, that got him to the island is Anthony Cooper (everything will be ok).

Anthony Cooper is not his father.