Gray lost his heart 5 years ago. Lucy, a mother, loves the children she had 5 years ago. Gray meets 2 children who looks exactly like him & were born 5 years ago. So what happened 5 years ago? Two people know: Lucy, but not Gray.
During a battle Lucy gets knocked into a coma, when she awakens she finds she was out for over three years. Lucy unfortunately lost her memory during her long slumber and causes Natsu and the rest of the guild to go into a panic.
But there is one major complication. That complication would be Amaya, a three year old girl who has been living in the guild, is currently parent less and is the spitting image of Lucy.