Likely a soldier from Navarro on the run from the NCR troopers actively hunting the Enclave and the Western Branch of the Enclave Remnants for deserting with his family.
He moved to Grayditch so that the NCR would stop chasing him, have a place to "put down roots" and have a safe place to raise a family. Ironically, he ended up moving to an even more dangerous area than before.
October 2, 2276: Brandice and his family arrive in Grayditch after having crossed the country from Navarro because he was trying to escape being captured by the Enclave, as he deserted them (having previously being an Enclave soldier).
October 30, 2276: He became concerned after scavenging a radio and hearing an Enclave broadcast that John Henry Eden recorded.
November 15, 2276: Dr. Lesko moved to Grayditch and offered Brandice caps to help build his shed, but Brandice declined.
February 24, 2277: He traveled to Megaton to buy a better gun because the fire ants were becoming more aggressive. It is hidden behind the refrigerator.