LOS ANGELES , California ( CNN ) -- Elizabeth and Mary Profit will not be taking center court at the U.S. Open women 's doubles final to face Venus and Serena Williams , but they share many of the athletic qualities that have made Venus and Serena the most dominant sisters in tennis history . Elizabeth Profit plays tennis while wearing an insulin monitor at her waist in this family photo . Elizabeth is 13 years old and holds a top ten ranking among 14-year-olds in Southern California . She is already defeating top-ranked players in the 18-year-old division . Her sister Mary , at 11 , is also a top-ranked player and dominating her age group . Mary won her first tournament at the age of 6 . Both girls started playing tennis as infants by hitting balls of socks across their living room . Their mother , Yvonne Profit , recognized their talent and saw it as an opportunity to develop sportsmanship and character and help them earn athletic scholarships at top national universities . So far , they have exceeded her expectations . In a sport that more often tends to develop players from affluent backgrounds , Elizabeth and Mary have already beaten overwhelming odds and endured the kind of adversity that too often ends in defeat . Watch how the sisters hope to achieve their tennis dreams » . The Profit sisters grew up in a single-parent household and trained with less than stellar coaches . They developed an exemplary work ethic to compensate for a lack of resources , Elizabeth said . Yvonne , who earned a degree at the University of Michigan , decided to give up her full-time job and move her daughters into an RV to keep up with the rigorous demands of traveling for tournaments . Elizabeth sleeps on a couch . There is a portable stove and shower . But the girls view living in an RV as an inconvenience rather than a hardship . The Profit sisters may be on a path toward a professional tennis career , but Elizabeth 's story off the court is just as compelling . She has juvenile diabetes and has been living with the disease since the age of 2 , when her body stopped producing insulin . Elizabeth learned how to test her blood sugar levels before the age of 3 and two years later , she began administering insulin injections on her own . `` My mom said I 'm not going use my diabetes as a disability , '' said Elizabeth . `` I 've got it for the rest of my life . And if they miraculously find a cure for it then that 's great , but I have to live with it . I ca n't make excuses . '' Until she learned how to manage diabetes , Elizabeth found herself collapsing at times . `` In this one particular tournament Elizabeth played in , her blood sugar was totally out of control and I kept hollering out to her , 'Quit ! Retire , you do n't have to do this , ' `` said Yvonne . `` She stopped and she turned around and said , ' I can do this . I can do this , Mom . ' `` Elizabeth went on to win the match and the tournament . `` By the time we got home , she had collapsed on the floor . And I said , 'Sweetie pie , why did n't you quit ? ' `` Yvonne remembered . `` Because you did n't raise me to be a quitter , '' Elizabeth told her mother . In spite of her diabetes , Elizabeth reached the No . 1 ranking in her age group in Southern California at 10 years old . Her sister Mary knows that diabetes can be debilitating and a matter of life and death , so she constantly watches over her older sister . `` Sometimes when I wake up to go to the bathroom , I check her blood sugar , when my mom 's sleeping , '' said Mary . `` Sometimes I wake up and give her something if her blood sugar is low . '' For the past ten years , Yvonne said , she has been unable to obtain private health insurance on the open market for her daughter because diabetes is considered a pre-existing medical condition . Elizabeth used to rely on a large insulin pump to make it through the day , but now she wears a small patch that releases insulin . Despite the inconvenience of checking her blood sugar level a dozen times a day , Elizabeth has not let diabetes deter her from achieving her goals . `` At 17 , I hope to see myself in the quarters of the U.S. Open like Melanie Oudin , '' she said . `` I hope to win some grand slams and get that No . 1 ranking . '' Elizabeth 's advice to anyone with diabetes is universal . `` I 'd say if you give up , you 're going to have to look back on your life and say , 'Oh I could have done this , I could have done that , ' `` she said . `` You do n't want to let life pass you by . You 're going to have so many years to live , so you might as well have fun while you do it . And once you die , you 're going to have a legacy behind , so make your life as fun as you can . '' Next year , Yvonne is planning to enter Elizabeth on the women 's professional tour , at the same age that Serena and Venus Williams turned pro .
Tennis star Elizabeth Profit , 13 , ranks high in her age group ; to turn pro next year . Elizabeth has juvenile diabetes , manages it ; ` ` I do n't make excuses , '' she says . Sister Mary , 11 , also a rising tennis star , watches over her older sister . ` ` You do n't have to let life pass you by , '' Elizabeth tells others with diabetes .