The Hidden Prince~ A Gratsu Fanfic
Long ago, an unnamed queen from an unknown kingdom ruled by "The Dragneels" ran away from the castle, leaving her two children behind. She went into hiding for a long period of time until she had met someone, who she soon fell in love with.
Years later, the two got engaged and the queen was pregnant with yet another child. The third child was named Natsu Dragneel, but had to keep his family name a secret, changing it to the father's. However, when the queen had given birth, she passed away, leaving her third child to the now lonely father.
Sixteen years have passed and the child has now grown. He inherited most of his mother's looks, including her body shape, yet possessed his father's personality. The father swore to protect his son in memory and promise of his deceased wife, keeping his status as the third prince hidden. Since then, the two lived normal and happy lives with one another.
But all that will disappear once they experience an encounter that will change their lives for good.