Gregory Eugene Allen was born to Gordon Eugene and D'Maris Anne Allen on October 30, 1968 in Austin, Texas. He attended Austin's John H. Reagan High School, and graduated salutatorian in 1987. In 1991, Greg received his Bachelor of Science in Electrical Engineering from University of Texas at Austin, graduating with Highest Honors. In 1993, he returned to The University as a part time graduate student. In 1998 he earned his Master of Science in Electrical Engineering. In 2011, Greg completed his PhD in Electrical Engineering.

Greg has been employed with Applied Research Laboratories (ARL) at UT's J. J. Pickle Research Campus since the summer of 1986, when he was hired through the High School Apprentice Program. Since 1988 he has worked on high-frequency, high-resolution sonar systems in the Advanced Sonar Group at ARL. In addition to design engineering, Greg has been involved in system-level testing, installation, and deployment aboard US Navy submarines, including a surfacing at the North Pole in 1993.

Greg has a daughter named Sabrina Fair, born in 1997. After two years of being a single dad, Sabrina was abducted to Mexico by her non-custodial mother in 2002. In 2014, she was found and returned the the United States.

In 2004 Greg married Mariana, his former Spanish teacher that he met in Mexico City. They live in northwest Austin and have three children of their own.