They look nearly the same age anyway. ARen't they only a few years apart? Or is Nick that much older? I honestly cannot remember. I don't remember much of FtWD, I'm afraid. Raven will likely take Alicia under her wing, given the circumstances. There will not be any jealousy to deal with coming from her with Alicia being the newest addition to the fold. Though this is starting to sound a little like a cult.
I adore those three. The new movies were fantastic in the portrayal and they did a perfect job of casting. As far as the game is concerned, I used the plot from Logan and went with Charles passing away a few years before the apocalypse. They would both be rather old in the present unfortunately so that's a time in her life she will never be able to get back. Raven and Erik clearly had some form of a relationship but that did not end pleasantly. Charles had feelings for someone else and only ever saw Raven as a sister so I kept that in, though I know that she kept a candle burning for Charles the entire time.