All sims in household age up

Dear people, dear developer, dear helper,

Everytime - no matter what save file I use - a sim ages up by blowing out some candles... the whole family ages up. I mean, the kid I choose to blow out the candles ages up first, but then within a few seconds the mom, dad, brother, sister and cat also ages up. This is really annoying. I can't do anything about it. It gets to the point where a kid ages up from kid to teen. Within a minute it becomes a young adult, adult and then a elder by only blowing out the candles once. 

Is this a reported bug, or are there any runaround fixes I could use? For now, it's annoying.

I have almost all the expansion packs + gamepacks etc. But this bug occured after I bought the High School Years EP. 

ah yes: I do use the normal lifespan. I haven't done anything since the purchase. The only thing I did was aging up a kid so I could discover the highschool.. but then this happened.