Are all of the stars in a constellation alive?

I am not sure what you mean with alive, but if a star isn't actively burning fuel, it's dead and you would not be able to see it. So in that sense all stars you see are alive. read more

No, none of the stars in a constellation or anywhere else are alive. It is useful for scientists though to think and write about: a star’s beginnings as its birth or starbirth; its longevity of burning (nuclear fusion) over long periods of time as its life or lifetime; and its (sometimes cataclysmic) ending as its death. read more

Given that a star like our Sun has a lifetime of about 10 billion years, many stars in most of the distant galaxies we observe died long ago. This cluster is 27,000 light-years away and lies farther than the center of our galaxy in the constellation Sagittarius. read more

The only star that does not belong to a constellation is the Sun. The Sun travels through the 13 constellations along the ecliptic, the 12 of the Zodiac and Ophiuchus. Among the remaining stars, the nearer ones exhibit proper motion, so it is only a matter of time before some of them cross a constellation boundary and switch constellations as a consequence. read more