Am I inadmissible?

HI
could u please confirm is my friend has to present his u k police report to local visa office for visit visa as other guys on board r saying "no"
And does his Canadian born wife could help in his visa application she is living with him with 2 kids since 1999.
And their intention is to visit Canada for no more than 1 or 2 months his wife has to sale out her inherited property there .this is very genuine purpose of his wife's visit to her own country she was born there and she wants to accompany with her husband and 2 kids.

Off course he will declare about his conviction if it is necessary to do so for visit visa otherwise he has no intension to work or live there for ever he has huge business in his own country.Regards