Question: What was the year of the death of David ben Maimon, the younger brother of the RAMBAM. He was on a business voyage when his ship sank.
Answer: Various biographies mention different dates for this incident, which was pivotal in the life of the RAMBAM. The Encyclopedia Judaica, 2nd ed (2007) states it ocurred in 1169. Joel Kraemer, in Maimonides: The Life and World of One of Civilizations' Greatest Minds, (2008) has provided two different calculations of the year.
One possibility is 1177: In a letter dated 1185 that Maimonides had written to a friend, Japheth ben Elijah, in Acre, he describes the terrible disaster of losing his brother 8 years before. (p. 255 and p. 545 note 46).
Another possibility is sometime just after 1169-1171, the probable time period that David wrote to the RAMBAM describing his upcoming voyage. (p. 252). However, Kraemer points out that perhaps this letter is describing a voyage prior to the ill-fated final voyage (p. 252).
David's trading business had supported the extended family. When David died, not only did the RAMBAM fall into a depression, but he also needed to find a new means of support (p. 257). He did not believe it was proper to earn a livelihood through his rabbinical duties. He instead devoted more time to his medical practice and became a renowned physician. At the same time he continued his illustrious scholarly career as a philosopher, jurist and community leader.