With DD1 we told most people, including our families, at around 13 weeks after we got the results of the 12w scan and screening tests. But we did tell one couple (very good friends of ours) at 8 weeks because we all went on holiday together, it was Christmas/New Year and there was no way we could hide that I wasn't drinking, was avoiding certain foods and needed naps every afternoon (1st trimester fatigue hit me like a brick, especially in the Australian summer). They were sworn to secrecy until we announced to everyone else later.
With this one we told our families at around 6-7 weeks, after we'd seen a good heartbeat. My mother and sister had moved to our city when DD1 was about 9 months old, so were around regularly and knew we were trying for a second, so hiding it for long wasn't going to work, especially since I had morning sickness for this one. Then I started telling my coworkers at about 8 weeks for safety reasons because I'd been put on insulin for early onset GD. We told our other friends as we saw them after that, and did a facebook announcement after the 12w scan again.