Her father is Michael Hennessey Higgins. Her mother is Anne Purcell.
Margaret Sanger's mother Anne was born in Ireland, emigrating to the US (via Canada) with her family. They were refugees from the Irish Great Potato Famine. Anne had 18 pregnancies in 22 years, resulting in 11 live births. She died at the age of 49.
Margaret Sanger, Anne's daughter, founded the American Birth Control League in 1921 which became, over time, the Planned Parenthood Federation of America.
"New York, New York City Marriage Records, 1829-1940," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:24ST-P2G : 20 March 2015), William Sanger and Margaret Higgins, 18 Aug 1902; citing Marriage, Manhattan, New York, New York, United States, New York City Municipal Archives, New York; FHL microfilm 1,570,821.
To Noah Slee
"England and Wales Marriage Registration Index, 1837-2005," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:QVZL-6QVQ : 8 October 2014), Margaret Higgins and null, 1922; from “England & Wales Marriages, 1837-2005,” database, findmypast (http://www.findmypast.com : 2012); citing 1922, quarter 3, vol. 1B, p. 1358, St. Giles, London, England, General Register Office, Southport, England.
"United States Census, 1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MZFY-9TN : 15 July 2016), Margeret Higgins in household of Micheal Higgins, Corning, Steuben, New York, United States; citing enumeration district ED 170, sheet 128C, NARA microfilm publication T9 (Washington D.C.: National Archives and Records Administration, n.d.), roll 0933; FHL microfilm 1,254,933.
New York State Census, 1905, database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:SPFN-87J : 26 November 2014), Maggie Sanger in household of William Sanger, Manhattan, A.D. 23, E.D. 20, New York, New York; citing p. 35, line 34, county offices, New York.; FHL microfilm 1,433,099.
"New York, New York Passenger and Crew Lists, 1909, 1925-1957," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:2H7L-M69 : 3 October 2015), Margaret Slee (Sanger), 1953; citing Immigration, New York City, New York, United States, NARA microfilm publication T715 (Washington, D.C.: National Archives and Records Administration, n.d.).