As of now you will take over a current family renaming their surname to the one you want to have.
what limits you and your freinds being in the same family is the family size. if the family you choose doesn't have the appropiate number of members then not all can join. Those that can join do so by family/child codes. these can be lock by you as youd be the head of the family. At creation they use the code and BAM theyre your family. However if you get breeding you should be fine eventually.