Serena and Venus Williams both booked their places in the third round of the Sony Ericsson Open with victories at Key Biscayne in Miami on Saturday.
World number one Serena did not sparkle but still had little trouble in her 6-2, 6-3 victory over compatriot Alexa Glatch.
Having dealt with the 19-year-old Californian, a wildcard entry, Williams will now play China's Peng Shuai, seeded 32nd, who beat Italian Mara Santangelo 7-5, 6-3.
Williams, who is seeking her sixth win at the Key Biscayne event, was far from happy with her performance.
"I definitely think I could have played better. But I had a few little jitters going out there -- no one wants to go out in their first match," she said.
Serena's sister Venus got off to a slow start but found her form to defeat spirited Israeli Shahar Peer 6-3, 6-3 and ensure a meeting with German Anna-Lena Groenefeld in the next round.
In the men's event, fourth-seed Andy Murray had to graft for his 4-6, 6-3, 6-2 win over Argentine Juan Monaco.
The Scot had his serve broken twice in the first set and then faced a 0-40 deficit in the first game of the second set, but fought back to hold his serve and then took a firm grip on the match.
"The only thing that matters really is winning," he said. "If I played great today and lost then I'm sure everybody would be pretty negative about it.
"I was really happy with the way I served. I thought that was just the key. I served a high percentage and got a lot of free points. When I really needed it in the second and third set then I found a big serve," he added.
"It's something in my game that's improved. I have to work on the rest of my game but I'm just happy I've got the chance to do that. I could have lost today," said the 21-year-old.
Murray will play Chile's Nicolas Massu, a three-set victor over American Mardy Fish, in the next round.
Another American Sam Querrey was knocked out by Spain's Feliciano Lopez 6-7, 7-5, 6-2, the number 32 seed firing 15 aces and breaking serve three times to set up third-round tie with compatriot Fernando Verdasco.
Eighth seed Verdasco defeated German qualifier Benjamin Becker 6-3, 6-4. The Spaniard lost his own serve three times but converted five of eight break point opportunities on Becker's serve.
Later, world number one Rafael Nadal opens his campaign against Russia's Teimuraz Gabashvili. In the women's event, Serbian third seed Jelena Jankovic is up against Argentine Gisela Dulko.
