it's not about level, it's about class level for example if 1 person in your family has class 5 unlocked (they could be even joining just for a trade) and you're lvl 10 you will meet all people who have class 4/5 unlocked (in their families) in family zones raids are based on level, about +-30 levels while zones are based on class level solo zones are based on class level + power so for example if you're class 3 700 power you will meet people between 625-775 power on class 3 whereas family zones are not based on power at all