I started out not singing tunefully. My voice was flat line the whole way. From birth I had hearing problems (corrected at 9 years old) and I was in a family of singers and musicians so I got condemning looks when I piped in incorrectly.   The pressure of other's abilities and the late start had delayed my singing.

At 14 I started taking piano lessons and learned to vocally imitate what I heard on the piano. By 16 I was taking guitar lessons and had learned to accompany my singing.

Listen, imitate and practice are the best things you can do.