Your physiology will affect the timbre of your voice and some singers are even born with vocal apparatus that naturally makes their voice sound incredibly good. However, there are many other factors apart from genetics that play a role in creating a good singer. You shouldn't lose hope if you think singing isn't in your genes. Becoming a good singer is a multifaceted process and there are multiple ways to become a good singer. Yes, genetics do play a pivotal role in determining your voice but they're not the be-all or end-all of becoming a good singer. Singing is a skill that you can easily learn too.