CUSTODY OF ILLEGITIMATE CHILD

I just want to seek advice regarding whom should have custody over my 7 year-old daughter. My ex-boyfriend acknowledged my daughter by signing at the back portion of her birth certificate. We shared custody & expenses over my child for 4 years (she was born on June 2008) but we broke up in January 2012. From that day, I have the custody and I am now the one who is giving all the needs of my daughter. Last May 2014, I got married to a different man and right now, I have a 2nd child, and together with my daughter, we live as a family. My question is, will he be able to get the custody over my child bacause I am already married? Please give me an advice on what to do to gain sole custody over my illegitimate child. Thank you!