The notion that Jedi are not allowed to have family's is something that came up after the Great Sith War (Exar Kun) when a great deal of the Jedi order turned on itself again. After that, the Jedi started centralising and becoming more dogmatic in an attempt to prevent something like that from happening again. This increased even further after the Jed Civil War merely some fourty years after. Still, there have been individual groups within the Jedi that have had other roles, such as the Corellian Jed and the Jedi Covenant.