You must have missed the Amnesty debates because one reason we cannot deport 20 million illegal aliens is because it will spit up families That's what the Amnesty forces proclaimed
I think you are confusing rethorical points used in the debate with actual legal arguments made before the immigration authorities or the courts.
It’s true that hardship and family unity are often cited as arguments by the defendant in deportation cases, but this hardly guarantees they won’t be deported as has been established by several well publicized cases.