Not sure what you mean. The phone and the tablet both connect to a wifi router, they don't connect to each other. What do you mean by "not let"? If you have a wifi signal available, the tablet should connect to it, whether the phone is there or not.
Is the router password protected? You might need to enter a password for it to connect to a certain wifi profile. That's what it sounds like to me, but I may be wrong. Would you happen to have wifi disabled?