The victory put Williams into the second round as she continues her recovery from Sjogren syndrome, an auto-immune disorder.

CNN: Serena makes winning clay comeback

Venus, who last won the U.S. tournament in 2004, is continuing her recovery from Sjogren syndrome, an auto-immune disorder.

CNN: STORY HIGHLIGHTS

The seven-time major winner plays Bethanie Mattek-Sands on her return to the tournament where she was diagnosed with Sjogren's Syndrome 12 months ago.

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