No future Astros, only former Astros with birthdays today ~
OF Nate Colbert (66)
Obtained by Houston from the Cardinals in the Rule 5 draft in 1965, Colbert was drafted from Houston by the Padres in the 1968 expansion draft. In the interim, he played in 39 games for Houston in 1966 and 1968. He went on to be a three-time All-Star for the Padres. For more on his incredible accomplishments for the Padres, read this Baseball-Reference piece.
IF Mike Brumley (49)
Originally drafted by Boston in the 2nd round of the 1983 draft, Brumley came to Houston as a free agent in 1993. He had a total of 29 plate appearances in 26 major league games for Houston in 1993 and 1995 (spending 1994 in Oakland). His minor league numbers in 1993 were quite impressive as he hit .353/.419/.471 in 96 games, but his composite batting average for the big league club was less than inspiring. He is currently the first base coach for the Mariners. For more about Brumley, read Bryan Trostel's Random Random Astros segment.
RHP Dennis Sarfate (31)
Sarfate, a 2001 9th round draft pick by Milwaukee, was purchased by Houston in September 2007 and was an Astro for a total of 8.1 innings before being traded away to Baltimore as part of the Miguel Tejada deal. In 7 games for Houston, he was 1-0 with a 1.08 ERA and a 0.720 WHIP. After three seasons in the Baltimore organization, Sarfate played for the Hiroshima Carp in the Japan Central League in 2011, going 1-3 with a 1.34 ERA and a 0.923 WHIP in 60.2 innings pitched over 57 games.