father abandoning his son

I have a nephew was abandoned from his father since he was 1 year old. My eldest sister and the guy is not married at all. When my nephew was born his fatheris not around and no chances to sign the birth certifcate to acknowledge my nephew as his son. After one month of my nephew, he appeared once, then it followed during the 3rd month and again only once. He left the country for his work as a seaman. When my nephew turn 1 he visit his son and after that he never come back again. We tried to reach him everywhere, we tried to talk to his family and relatives, but no one from them wants to give any information about the guy. After 4 years my sister found out that the guy already got married. Again, we tried to search him even in social networking but he blocked all the person including my sister and all who is related to her. Now, my nephew is 13 years old. I just want to ask if there is a chances to file a case against the father of my nephew for abandoning his son and never doing his responsibilities from the start until now. If ever, what kind of case we can file. Thank you very much