Unfortunately (or fortunately, depending on perspective I suppose - lol), I've also seen this first-hand. Aliens seem to frequently want to take my sims for trips (and usually more). I'm not disappointed though. It kind of makes things interesting. Although, a bit chaotic. hah!
An example is what's going on in my latest save: I'd gone w/o aliens for about...a couple of weeks of gameplay. All of a sudden, my grandpa sim gets taken. Then, Grandma. Then gramps again, this time with a little "present". Moved the grandson out after he married and aliens got him and gave that household a bundle of "joy", switched households back to a friend of theirs that started this save, and after the friend was married, her husband was taken and impregnated also. It's the 100 baby challenge--alien edition and I didn't even initiate it. :D :D