Conversation so far:
When was Daniel Barenboim born?
Daniel Barenboim was born on 15 November 1942 in Buenos Aires, Argentina.
Who were Daniel Barenboim's parents?
Daniel Barenboim's parents were Argentinian-Jewish Aida (née Schuster) and Enrique Barenboim.
Are there any other interesting aspects about Daniel Barenboim?
Daniel Barenboim holds citizenship in Argentina, Israel, Palestine, and Spain, and was the first person to hold Palestinian and Israeli citizenship simultaneously.
Did Daniel Barenboim have any children?
Daniel Barenboim had two children.
What did Daniel Barenboim's wife do?
Daniel Barenboim's first wife was a cellist. His second wife was a pianist.

Question: Who was a witness to their marriage?
Self-contained rewrite: Who was a witness to Daniel Barenboim's first marriage?