Thats what i was told yes i could get a 6th phone, but on a separte plan not with my 5 shared plan. So what the point of getting a 6th phone from sprint then... been a customer for over 10yrs.
There are always possibilities (I have seen 6 line accounts), but expect complications if you get someone who tries to add a 6th line (I have seen accounts get truly messed up beyond recognition). The plans are only designed to go up to 5 lines sharing and are limited to that number, more than that and any time you try and change anything on the phones the entire thing could come crumbling down. If you need more than 5 lines sharing you should setup the account as a business instead under a Tax ID and use the Business Advantage plans which have no limit on he number of phones sharing.
I don't know of a single carrier that allows more than 5 lines on a family share plan regularly, the major 4 carriers all have a limit of 5 phones.