UPDATE June 4th, 2015: An alternative (alt) version of this mod is now available!
Just like the original, this version will ignore the relations between step-siblings. As far as the game understands it, with this mod step-siblings are just perfect strangers to each other, and can get as romantic amongst themselves as they like!
But un-like the original, this version is supposed to still recognize step-parent/step-child relationships, so a sim will still be able to encourage their step-children (or any other parenting options that might depend on this test). This also means that romance between a sim and their step-parent or step-child will NOT be possible.
UPDATE September 18th, 2015: I've decided to declare the test phase succesfully completed. I think the alt version is safe to use and does exactly what it *should* do: 110 downloads so far, and no bug reports. And in my own game it has been performing splendidly as well.
Filesize 561 bytes | File Name BO - Step-Family Romance (alt).zip | # of Downloads 611