The Latvian player advanced to the fourth round at the French Open on Friday, beating Radek Stepanek of the Czech Republic 6-3, 6-2, 7-5. He was asked about his siblings after the match.
"I wouldn't like my sisters to become professional tennis players. It's [a] tough choice of life," Gulbis said. "A woman needs to enjoy life a little bit more. Needs to think about family, needs to think about kids."
Gulbis went on to say that life on the tennis tour is difficult, more so for women who want children.
He said female tennis players can't think about having kids until they are in their late 20s, and "that's tough for a woman, I think."
Maria Sharapova, who also advanced to the fourth round on Friday, played down Gulbis' comments.
"I don't think we can take everything serious when he speaks," Sharapova, 27, said with a laugh. "I think he's great entertainment and we love to listen to what he has to say. But, I mean, of course, you have different opinions.
"In a way, I think he was joking, but he's playing the sport, so how bad can it be? If he felt so bad about it, and even if he's a male, I don't think he'd be playing it."
Novak Djokovic chose to stay out of the fray.
"Everybody is entitled [to] their own opinion," Djokovic said after his third-round victory. "I respect his opinion, and I respect everybody's opinion, but I can't say more than that, really."
Gulbis will be playing in the second week of a Grand Slam tournament for the first time since reaching the quarterfinals at the 2008 French Open. He will next face 17-time Grand Slam champion Roger Federer.
Gulbis: A Woman Needs To 'Think About Kids'
Ernests Gulbis addresses the press and is asked if his younger sisters, who also play tennis, may become professional tennis players one day.