Question:  Ronald de Boer is the older twin brother of this Dutch former footballer born in what year?

Context paragraphs:
Teuntje de Boer: Teuntje de Boer (born 31 May 1968) is a Dutch former cricketer.  She played fourteen Women's One Day International matches for the Netherlands women's national cricket team.  She was part of the Netherlands squad for the 2000 Women's Cricket World Cup.

Michael Johansen: Michael Bro Johansen (born July 22, 1972) is a Danish former professional football player who played as a midfielder in the Danish Superliga for FC Copenhagen and for English club Bolton Wanderers.  He played two games for the Danish national team in 2000 and 2002, and was an unused substitute at the 1992 Summer Olympics.  He is the older twin brother of former footballer Martin Johansen, and played alongside him in several clubs.

Frank de Boer: Franciscus "Frank" de Boer (] ; born 15 May 1970) is a Dutch former footballer and manager.

Ronald de Boer: Ronaldus "Ronald" de Boer (] ; born 15 May 1970) is a Dutch former football midfielder who played for the Netherlands national team as well as a host of professional clubs in Europe.  He is the older twin brother of Frank de Boer.

1998–99 FC Barcelona season: During the 1998–99 FC Barcelona season, the club once again retained the La Liga title, but eliminated by Valencia in the round of 16 of Copa del Rey.  Barcelona enjoyed a great season with their new signings Ronald de Boer, Patrick Kluivert, Frank de Boer, Mauricio Pellegrino, Boudewijn Zenden and Phillip Cocu.  Barcelona's league start was slower in early season but Barcelona turnaround to secure La Liga in late-May, but Barcelona crashed out of the UEFA Champions League, following an another lackluster performance in the First Group Phase.

Alexander Schenk Graf von Stauffenberg: Alexander Franz Clemens Maria Schenk Graf von Stauffenberg (15 March 1905 in Stuttgart – 27 January 1964 in Munich) was a German aristocrat and historian.  His older twin brother Berthold Schenk Graf von Stauffenberg and youngest brother Claus Schenk Graf von Stauffenberg were among the leaders of the 20 July Plot against Hitler in 1944.

Yentl en De Boer: Yentl en de Boer is a Dutch cabaret and musical duo, consisting of Yentl Schieman and Christine de Boer.  In 2015 the duo received the "Annie M.G. Schmidt Award 2014", awarded to the best theatrical song of the year, for their song "Ik heb een man gekend" ("I knew this guy").  Earlier on in their career Yentl en de Boer was awarded the Wim Sonneveld Award and the Audience Award during the Amsterdam Cabaret Festival 2013 ("Amsterdams Kleinkunst Festival 2013").  Yentl en de Boer are praised for their harmonious vocals and witty lyrics.

Orlando Trustfull: Orlando Trustfull (born 4 August 1970 in Amsterdam) is a Dutch football manager and a former professional player.  He was the assistant manager at Internazionale and was brought in by Frank de Boer.  As of the start of the 2017–18 season he joined de Boer as a member of the coaching staff at Crystal Palace.

1995 Dutch Supercup: The match for the sixth Dutch Supercup was held on 16 August 1995 in the De Kuip in Rotterdam.  The match featured the winners of the 1994–95 Dutch first division, Ajax, and the winners of the 1994–95 KNVB Cup, Feyenoord.  This was the third year in a row, that the Dutch Supercup involved these two teams.  The games was won by Ajax 2–1 after extra time, with the Ajax goals coming from Ronald de Boer and Patrick Kluivert, and Henrik Larsson scoring for Feyenoord.  This victory meant Ajax had won the Supercup three years in a row.

Yvo de Boer: Yvo de Boer (born June 12, 1954) is an advisor and consultant on international environmental policy.  De Boer is the former Executive Secretary of the United Nations Framework Convention on Climate Change (UNFCCC), a position he held from 2006 until 2010.  After his UN tenure, de Boer was Global Chairman of Climate Change and Sustainability Services at KPMG.  From 2014 to 2016 de Boer was Director-General of the Global Green Growth Institute (GGGI), a Seoul-based international environmental organization.

Supporting paragraphs: Ronald de Boer Frank de Boer
Answer: 1970