No!! People that knew Vaughn's father are always saying that Vaughn looks just like his dad. There is no way that Sloane is Vaughn's dad he doesn't look like Vaughn at all!! Unless Sloane is a double from many years ago or had plastic surgery!! A lot of it!!
No, I do not think sloane is Vaughn's dad. If anything, he's Sydney's dad. there's a thread about it and some REALLY good points are given for example:
1. Sloane calls Syd 'his greatest acomplishment'
2. Sloane and Irina are now presented as a team.
3. At the end of Season one, syd talks to Sloane about if he ever thought about having children and it sounds like he's talking about her if you think about it!
4. he says often (or SAID) that he considers her his daughter...... pretty strange
I think it's possible that Sloane is Syd's father (although I hope not...that would COMPLETELY shatter Jack!)...I don't see any reason to believe he might be Vaughan's dad...if you have any evidence I'd be more than interested in seeing it!