Steven is the adopted brother to the crystal gems?

i kept looking for other imformation on steven universe and then i found this "Guardians of the Universe known as the Crystal Gems. He is also the proverbial little brother to Garnet, Amethyst, and Pearl" so does that mean that rose quarts was the mom of all of them? or did she adopt pearl garnet and amathest or did they adopt steven but they didn't really think of themselves as mothers so they decided sisters? i give this a rating of 3 out of 5 what do you think?