A Son From Another Mother

So I just had my dad and his wife here for a week. On the very first day of the visit Dave was doing some yard work and my dad was outside enjoying the weather and most importantly smoking his cigarettes.

Unbeknownst to me...my dad had disclosed a very important fact that could be life changing.
After dropping my dad and Ellen off at their hotel that evening, Dave had mentioned that my dad had said something 'strange'. It was said in such a way that Dave was uncertain if my dad was joking or if he was seriously disclosing truth to him. My dad had told Dave that he had a forty-six year old son from another mother. Oh and yes he shouldn't say anything to anyone else meaning me.

Of course Dave wasn't going to keep something like that from me. Dave had disclosed this huge information to me and then I had to choose what to do with this information. So now what do I do? Do I get Dave to probe more? Do I confront my father immediately regarding this information? Or do I ask Ellen about this information? But what if Ellen doesn't even know? Ellen's children are older than forty-six so it wouldn't be one of her son's. So who is this other woman?

So how does this information affect me? Does it make any difference at all knowing that I have a half brother. Where is he now? Does my dad have any contact with this son? He obviously has seen him because he knows it was a boy.

The initial thought is that my brother Paul would be forty-six years old. I'm pretty sure that Paul was my mother's son so no it wouldn't have been Paul that he had been talking about.

This was pointing towards the likelihood that my father had another affair. Great thing to learn about your dad. That wasn't a complete shock to me since he already had one affair.
At my dad and Ellen's wedding, I found out that they had been together for twenty-one years and I was only nineteen at the time. Who's to say he wouldn't have had another affair?

You hear about other families learning that someone was adopted or that you had a twin somewhere. But you never expect your own family to have someone that you are unaware of.

So now I was waiting for the appropriate time to talk to my dad.