Game version 1.114.46.1030
Mods - [adult mod mention removed] and Relationship & Pregnancy by Lumpinou, that's all.
All the abductions took place in Chestnut Ridge, but on different lots. Four families live in this town, and I play them most often. There are two more families in other towns, but they haven't been abducted.
The first abduction was of the Sim's mother, but she didn't get pregnant. Then, some time later, the father was abducted, but he also didn't get pregnant.
Then their daughter moved to another lot, and after a week, she was abducted, got pregnant, and gave birth. Since then, her husband has been abducted on this lot about five times over several weeks.
Then this family moved to another lot, where they were also pursued by aliens. It happened that three nights in a row, aliens would come and try to kidnap the man, but I would reset him (reset the sim using the shift key). Yesterday, while playing, this Sim's brother was kidnapped on another lot.
So, every time I play families in Chestnut Ridge, a Sim gets kidnapped at least once.
(Translation via Google Translate)