Until your daughter's boyfriend changes his address on his insurance, driver's license and vehicle registration it may be that your insurance company requires you to add him as an exposure in the manner your agent noted since it does appear that he resides at your home.

With him having so many items stating that he does live at your residence it would be difficult to prove that he did not live there so it is likely your insurer is trying to look out for your interests and the liability or exposure of the insurance company as well.

If you are uncertain if this is the best choice for you try shopping around with other insurance companies to see if they offer up a different solution. You can also contact the Texas Department of Insurance's consumer division to see what advice they could give you in this situation and if what your agent is suggesting is a good idea or not.