Who is Ash's dad? I've heard suggestions like Oak, Giovanni, random travelling trainer and even (sickos) Ho-Oh, I personally think it's Giovanni, but I don't read the anime, so the answer might be there?

Well I think he hasn't met his father yet.

You could check Bulbapedia

But if he has met his father I think it'd be Giovanni but that would make Silver his brother...

If you ask me, I think Ash's dad will never be shown. This is because (if you want my thoughts) His fauther left on his pokemon journey. When he was in the orange islands, he was the 'chosen one' to collect the treasures. Then, at thunder island, he got fried by Zapdoes *people stare* ........ dont ask. I just made that up now