Chris Kent: While he could still exist it's unlikely that he's in the family as the adopted son of Kal-El since he's not married to Lois anymore. While I'm not sad to see the rapid aged "Nightwing" section go I do miss little Chris. I liked the idea of Clark and Lois not only adopting a child like his earth parents did but the twist of their sons' birth parents being his villains. Chris was cute but never really had much spotlight time.
Lena Luthor: I'm likely the only one who cares about this but ever since I discovered her I loved the idea of Lex being a doting father. Lena showed how complex Lex could be, yes he still put things before her but she was still the most important person (besides himself) in his life. Like all the characters on this list she had a lot of potential that was never explored. If she was around when it was discovered that Lex was the human donor for Connor then it would have been fun to see the dynamics.
Iris West and Jai West: I'm not a big Flash fan, the most I've read of any Flash was with Bart Allen but I was fond of these two and looking forward to seeing how they worked with the family. But with Wally not appearing and the rest of the kids disappearing to make the old guard look younger it seems unlikely that they exist anymore. Although Bart's around so Barry is still a grandpa.
Lian Harper: Lian was my favorite out of the kids listed here. Even so I'm a little split on her currently not existing. After what happened when they killed her off I'm willing to read stories about Roy not being a father because let's face it, they have to build him back up to us even if this is new canon. And although there was no plans for her to be born at present I like the idea of them playing with it a little differently. Roy wasn't there when she was born the first time, he could be here.
Rani (Carter?): I'm not sure how I feel about Rani as I wasn't fond of how her presence changed Michelle or most of the Giffin/DeMatteis run on Booster Gold. But I like the idea of a kid with an unclear future. I like the potential of adding depth to Michelles' character (if written right) and exploring Boosters' own feelings on parenthood before little Rip comes into the picture. And I always thought it would make sense for a hero to adopt a kid from such a scenario. I'm just not sold on how it's written or the idea of making Booster a parent when he clearly isn't ready for it (plus how he got guilted into it in the first place.)