I don't know if this is really the behavior that should be happening so I'll just bring it up for discussion. My paternal grandfather is adopted and that is indicated in my family tree, but I have a few generations of his adopted family in my tree because my aunt has always suspected that it was an "in the family" under the table adoption. We are 99% sure that what his mother told him about his birth and adoption was a bald face lie. In the last couple days I've gotten 2 common ancestor matches with this adopted family line.

At this point you're thinking, great you've got evidence your aunt was right! Not quite. My dad also has done ancestry DNA and does NOT have these matches. In fact, I have over a dozen matches that trace to my paternal (adopted) great-grandmother's family. And my dad has none. At this point I think I'm probably more closely related to my dad's grandmother than he is just through my mom's line not his.

So I'm wondering if adopted lines should be included in the DNA matches or if this is a bug.