There's a lot of love on the tennis court lately, and not just in the score.

Sisters Serena and Venus Williams have played each other in three of the past four Grand Slam tennis finals, and although they are ranked No. 1 and No. 2 in the world respectively, it's their sibling rivalry (or lack thereof) that garners so much attention.

After each final, no matter the winner, the sisters hug and gush about how happy they are. But some feel the lack of claw-out-your-eyes competition is hurting the game and fans' level of enthusiasm.

"Any time the two sisters play together it's really boring," said Edward Wong, 40, of New York City, who plays tennis regularly and enjoys watching the pros. "When they play others, you can see the fire in their eyes. ... But when they play each other it doesn't look like they try their hardest. It's really uninspired tennis."

But others think the siblings' lack of bloodlust is only natural.

"It's hard to look across the net and want to beat the pants off of your sister," said Chris De Maria, vice president of communication for the Women's Tennis Association. "McEnroe used to say it was very hard for him to play his brother Patrick."

There have been other sibling rivalries in tennis; the McEnroes, the three Maleeva sisters and the Gullickson brothers -- but none can touch the history-making matches of the Williams.

In such high stakes matches there's little room for holding back. But both Williams sisters have discussed the difficult balance between the urge to win and their loyalty to each other.

For Venus there is the conflict of trying to win, but also wanting Serena to win "because I want the best for her." And Serena, the baby of the five Williams children, says she also wants to win, but doesn't want to overshadow her big sis.

"At the end of the match, if I win (against Venus), I'll feel really bad," Serena told the Associated Press. "I know Venus has beaten me a few times. She felt bad. When I beat her at the French Open, I kind of felt like I wished there was something that she could have won, too."

After Serena beat reining Wimbledon champ Venus this year, hugs were exchanged, and older sis snapped photos of Serena hoisting her trophy into air.

"What I can't seem to grasp is how their brilliant father was able to instill a level of competition in them that grabs for the jugular, while at the same time eliminating the innate sibling rivalry that has been in existence since the dawn of time," said tennis enthusiast Kristina Malcolm, 28, of San Francisco, Calif.

How siblings handle rivalries depends greatly on parenting, according to Dr. Ronald Kamm, president of the International Society for Sport Psychiatry.

"Richard Williams has bred an 'us-against-them' mentality in the girls -- be aggressive against anyone else, but you are sisters, and if your sister beats you you're going to support her," he said.

"I think there's a lot of pressure from him on them to not openly criticize each other, or break rank. And that's fine. In a healthy family you want to be able to deal with competitive and jealous feelings."

While their tepid inter-family play has some fans turning the TV off, experts say for now Serena and Venus are a hot ticket.

"Nobody wants to see the Yankees win 20 championships in a row, but at this point it's good for the game," De Maria said. "(The Williams) are attracting new groups of fans, are good for TV ratings and great motivation for children."

But fans like Wong say it doesn't matter who's across the net. He doesn't hold back against his steady competition -- his wife -- and neither should the pros.

"When I get on the court, I get on the court to win."