So glad when I found this out. Patton Oswalt has been missed on this show for a while now, so it'll be good to revisit the Koenigs, even if it is one of their ancestors (grandfather?). I imagine this'll be the only Oswalt/Koenig appearance in the season, as shows with their final seasons like to bring back a lot of characters for an episode, so this'll likely be that.

Patton OsWalt Special Guest star will come back to Agents of SHIELD in season 7 I cannot wait

I love your theory on being their grandfather, like maybe the first S.H.I.E.L.D. agent in the family. I am just imagining how funny the scene could be- this could also be the way he Koenig family gets involved in S.H.I.E.L.D. in the first place!