What a beautiful thing it is that you now recognize that your father was saying "hello" to you.
And for your brother-in-law to have requested that song for their wedding without knowing the history behind it, well....just proves that certain sentiments are so strong that they can be carried on in families. Yes, I'm sure that request brought your father and brother-in-law closer. What a blessed feeling they both must have shared.
I know our loved ones are never far away, even after they leave our realm. The "hello" from your dad must have brought you a feeling of great warmth and comfort. Good