Country music star Holly Williams is set to become a first-time mum.

The singer, who is the granddaughter of music legend Hank Williams, and her husband Chris Coleman are preparing to add another member to the famous family this October (14).

Williams fittingly took to on Mother's Day in America (11May14) to share the good news, posting a photo of herself aiming a rifle while showing off her growing baby bump.

The accompanying caption read:, "@colemantime (husband) caught this of me while shooting tin cans this morning on the Georgia farm. I think I felt my first kick and I’m not talking about the Red Ryder Bb gun!!"

Williams wed drummer Coleman, who tours with Kings of Leon, in 2009.

She tells that she didn't expect to fall pregnant so quickly after she and her husband decided to start a family.

She explains, "I’ve had so many friends who’ve struggled with infertility issues, so I thought, 'Well, this could take five years'. And it didn’t at all! We felt really blessed. It was like the Lord gave us this little miracle."

Williams, who is outspoken country star Hank Williams, Jr's daughter, is due on 9 October (14).