It's really up to you when you tell your family members you're pregnant.
But I would wait at least until you're 5 or 6 months into the pregnancy before announcing it to extended family and then again if you don't want to tell the family members that you're pregnant then there's no requirement for you to do so.
Personally when I became pregnant I only told my parents and sister and didn't tell anyone else in the family.
But my parents and sister told the other extended family so I didn't have too.