Sorry, I just went through your post history - this is regarding your future son in law, not you? They have no prospect, I'm afraid, of living together in Canada in the near future, for the reasons above (if he's criminally ineligible, he isn't able to apply until 5 years after he's paid the fine), nor is he legally able to enter Canada even as a visitor (and I hope he's never lied on an eTA app, or to a CBSA officer asking if he's ever been arrested, because that would introduce a whole new level of complications). I don't know anything about what the rules are for Australia, but if he and your daughter want to live together, it's going to have to be there, or a third country which will take them both.
. He was in Canada, didn't mention the traffic violation on the eTA before he came because he didn't even think about the traffic offence, as they have "spent" charges, which equate to a pardon in Western Australia, and they aren't obligated to divulge any spent convictions even when asked (except in rare instances like dealing with children, government jobs). I'm not excusing this behaviour at all, I am just trying everything to keep my daughter here - I'm upset about the eTA, (I've no idea what implications that would now mean for a PR app), and the non-payment of the fine (he'd moved abroad so didn't pay) which is why I asked about visa officer discretion - or a good lawyer - but I guess there's no discretion and no hope for at least 5 years now. Ugh!