Question: When was Ann Walton Kroenke's only sister born?

Context paragraphs:
Ann Fox: Sister Ann Fox (born Jeralee Ann Fox in 1933) is a Roman Catholic nun, social activist and expert in educational enrichment.  She is co-founder and previous executive director of the Paraclete Foundation.  She teamed with Barry T. Hynes to create the Paraclete Foundation to provide educational enrichment for at-risk children in South Boston.  The Paraclete Foundation, along with South Boston mothers known as the Stella Maris Group created the Paraclete Academy in 1997.  The academy is housed in the former St. Augustine’s convent.  The Paraclete Academy focuses on elementary and early middle school aged, at-risk children.  The Paraclete Academy provides after school enrichment programs in the South Boston community that aims to erase the education disparity between inner city children and their more affluent peers.  By Sister Ann’s retirement as executive director in 2012, nearly 1,000 local children had participated in the Paraclete Academy’s programs and over 70 young college graduates had volunteered as full-time teachers in residence.

Joseph Cotton: Joseph Cotton a.k.a. Jah Walton (born Silbert Walton, 1957, St. Ann, Jamaica) is a reggae deejay active since the mid-1970s.

Nancy Walton Laurie: Nancy Walton Laurie (born May 15, 1951) is an American heiress to the Walmart fortune, businesswoman and philanthropist.

Ann Walton Kroenke: Ann Walton Kroenke (born December 18, 1948) is an heiress to the Wal-Mart fortune.  Kroenke and her sister, Nancy Walton Laurie, inherited stock from her father, Bud Walton (died 1995), who was brother and an early business partner of Wal-Mart founder Sam Walton.

Alice Walton: Alice Louise Walton (born October 7, 1949) is an American heiress to the fortune of Wal-Mart Stores, Inc. She is the daughter of Wal-Mart founder Sam Walton and Helen Walton, and sister of S. Robson Walton, Jim Walton and the late John T. Walton.  With a net worth of $40.8 billion she is the wealthiest woman in the world, according to "Forbes", following the death of Liliane Bettencourt in September 2017.

Joan Evans (charity worker): Sister Joan Evans, PBVM is a retired Australian religious sister born in 1931 who was based in the Klong Toei slums in Bangkok, Thailand.  She is a member of the Western Australian Congregation of Presentation Sisters.  Sister Joan is a charity activist, who helps the needy youth and families in the slums of the Thai capital.  Each fortnight, Sister Joan's project supports around 100 babies with deliveries of powdered milk.

Whitney Ann Kroenke: Whitney Ann Kroenke (born September 29, 1977) is an American heiress, film producer and philanthropist.

Fred Fassert: Fred Fassert (born 1938) is most famously known as the writer of the popular song "Barbara Ann," which was originally written for the band that he was in at the time, The Regents.  In 1961, the song reached #13 on the Billboard Hot 100 chart.  It was covered by other artists, including the Beach Boys on their 1965 album, "Beach Boys' Party!" , with the single reaching #2 on the Billboard chart.  Fassert wrote "Barbara Ann" for his sister, Barbara Ann Fassert.  His brother, Chuck Fassert, was the original 2nd tenor of the Regents.

Mary Todd Lincoln: Mary Ann Todd Lincoln (December 13, 1818 – July 16, 1882) was the wife of the 16th President of the United States, Abraham Lincoln, and was First Lady of the United States from 1861 to 1865.  She dropped the name Ann after her younger sister, Ann Todd [Clark], was born, and did not use the name Todd after marrying.

Waggoner Ranch: The Waggoner Ranch is an historic north Texas ranch located 13 miles south of Vernon, Texas.  The land was used primarily to raise crops, beef cattle and horses as well as for oil production.  It was notable for being the largest ranch under one fence in the United States.  It was originally established in 1852 near Vernon, Texas by Daniel Waggoner under the name of Dan Waggoner & Son; his son being William Thomas Waggoner.  It was acquired by Stan Kroenke, who is married to Ann Walton (niece of Sam Walton), in February 2016.  At the time of acquisition, the ranch comprised 520,527 acres , or 800 mi2 but additional acreage was included in the sale making the total closer to 535,000 acres .

Supporting paragraphs: Ann Walton Kroenke Nancy Walton Laurie
Answer: May 15, 1951