of which/whom

Although people have become rather casual about such things, mere courtesy suggests that you use whom, rather than which, as your father is a person, rather than a thing.

I would go for 'whom' as it is used for people whereas 'which' is usually used for objects.

The problem is not that people have become casual. That's unmitigated drivel. The problem is that there are people who try to give advice about language when they don't know much about how it works.

'which' sees use in English for people when the referent is rather general.

Both 'which' and 'whom' work just fine.

And, if I were to throw in my 5 yen's worth, I'd take the 'which' and get your money's woth out of it . . . because language is fluid, and that's more so the 'sign of the times.' 'Whom' is too straight-laced--IMHO.