I'm glad you figured out a work-around, now you can have a family reunion. Did you can make them brother and sister in cas with the cas.fulleditmode cheat?
I tried giving them the sibling relation in CAS, but it was not possible. I've not done much in CAS this year, but it used to be possible adjusting family relations only if at least one of the sims were never actively played. Maybe I played the family before saving to album, or maybe that household was too old (speaking 6-8 RL years). Not the biggest problem in the world though, my game will go on :)
