Well, anything with Vader and Luke/Leia will work, so you've got plenty of options there. You can do any of the Han's with 3 different pieces. Too bad we don't have a Ben Skywalker yet.
I'd be tempted to let Jag Fel and Roan Fel slide. We don't know for certain how that plays out, but the timeline fits without too much effort. There might be one more generation in there, but it's hard to say. But Baron Fel and Jag Fel would definitely work. Pilot squad?
You could also allow Grandfathers and their Grandchildren, or Great Grandfathers etc. That would open up a lot. Vader or Luke with Cade. Vader with Jacen/Caedus or Jaina. I mean, technically you wish your grandparents a Happy Father's/Mother's day too sometimes.
LOL, you could allow Sidious and Vader together if you want to believe the speculation that Sidious manipulated the Force/midichlorians to create Anakin.
And my final silly idea. IG-88 and IG-88 BH together, since technically, there was only one IG-88 to start with, and he created 3 more. I mean, it's really not much different than Jango and Boba or the clones.