Well personally I think it is an improvement not a bug since now aliens that don't have the same mother (the sim male that gave birth) can now have romantic relationship between each other since they do not show as brother and sister anymore, unless I am mistaken.
It's not an improvement, as far as I'm concerned. I already had that problem fixed with the Multiple PT hack, so each alien spawn was siblings with maybe one out of eight of the other alien spawn. Now they aren't related to any of them, which is annoying, and I can't tell which PT they're the spawn of, and I suspect it may be connected to the hack not working at all anymore.