From: Rabbi Moshe Sofer
To: Rabbi Aryeh Leib Fox
A man was found drowned eighteen days after disappearing, with no witnessed declaration of suicidal intent. The Chasam Sofer rules that without such evidence he cannot be classified as me'abed atzmo lada'as, and mourning is permitted both on its own merits and to preserve family honor. Kaddish may be recited by the children as a right derived from their communal partnership in its recitation, regardless of any residual doubt.
Source: Shu"t Chasam Sofer YD §326