Serena Williams' sister Venus is "super excited" to be an aunt.

Serena Williams

Serena Williams

The 35-year-old professional tennis player welcomed her daughter - whom she has with her fiancé Alexis Ohanian - into the world on Friday (01.09.17), and her older sister and fellow tennis star Venus, 37, is thrilled to become an aunt to the new arrival

Speaking to ESPN at the US Open, Venus said: "I'm super excited. Words can't describe."

Speaking after her third-round match win against Greece's Maria Sakkari, Venus claimed she wouldn't be answering questions about her sister's start to parenthood, but did admit the pair "always talk".

She said: "We always talk. We always talk, so she's always encouraging me. Yeah, from every step of the way, every match, always."

Serena reportedly gave birth to a baby girl weighing in at 6 pounds, 13 ounces, at St. Mary's Medical Center in West Palm Beach.

Meanwhile, Serena previously revealed she is "looking forward" to motherhood.

She said: "I am looking forward to becoming a mother and coming back to the courts already. I'm always thinking about what's next: the next victory, the next trophy ... I intend to keep exercising for as long as possible while pregnant.

"I want the baby to be healthy and for that you need a healthy life. Also, when I come back to tennis it'll be better if I've kept as fit as possible all the way through the pregnancy rather than having to lose a lot of weight afterwards in order to get fit again. Eating healthily is a must, but being healthy is a lifestyle."

The sportswomen also previously revealed she thinks having a baby will make her a "real woman".

She shared: "I have so much respect for so many women [for giving birth]. I am about to be a real woman now, you know? It's going to be something incredibly impressive to go through ... I don't think watching birthing videos helps. I actually think it makes it worse. Having a baby, nothing is guaranteed."