Maybe bro maybe...but how will knowing whether or not these stars are Muslims, benefit us? In fact, May Allah protect us, by wasting time trying to find out about their place in Islam, we can commit bigger sins and even lose our Islam, due to our lack of knowledge on things that are far more pressing.
But yes you are right, being born to a Muslim family does not make one a Muslim, and I know this firsthand, sadly, due to the state of my own family and who I was less than ten years back, Astaghfirullah!