Been there, done that! It's what is so rough about 15 weeks - you think you're out of the woods, you tell everybody, then have to untell them :-(. I was happy that my family knew though, because to be honest, I was so sick and weak afterwards it would have been hard to explain and we would have had to tell anyway. I needed their support, and it would have felt awful if it had been some deep secret.
In our case, we told my family early, around 8 weeks when we had our first scan. DH told his family at 12 weeks. Our parents live in different cities and have no contact, so it was unlikely to ever come up that they were told at different times, nor would they care - none of them are dramatically inclined, and despite their excitement they all respect that it's *our* news, not theirs. At the end of the day, unless you're maliciously withholding it from somebody as part of a power play, I really think when you tell is up to you. There's no entitlement for them to all know at the exact same time. (Btw, I'm currently 10 weeks with pregnancy #2... Only DH, my boss, and 1 of my sisters know. I'm holding out to the 12 week scan this time!! It just feels right to me. I don't want to start getting all of the pregnancy advice and judgment too soon!)