Insomnia/lack of sleep could be due to many reasons..in your uncle's case obviously the stress
of separation seems to the most likely cause. But lack of sleep and murmuring do not by themselves amount to the label of depression
, for which there must be other associated symptoms. Also we have many other labels like adjustment disorder
etc etc which may present with same symptoms. Fixing a label, finding an appropriate help (either with medicine or talking therapy and other social activities as mentioned above by my colleagues) can be best done only after a thorough assessment. Please do consult a psychiatrist
Good Luck to both of you.