Wikipedia is pretty good on this sort of stuff. Singer Cissy Houston (mother of Whitney) was named Emily Drinkard when she was born in 1933. Houston's singing career began in 1938 when she joined her sister Anne and brothers Larry and Nicky in the gospel singing group the Drinkard Four. Lee (who would later become the mother of singers Dee Dee and Dionne Warwick), later joined the group along with Ann Moss and Marie Epps, and the group was renamed The Drinkard Singers. Houston and the Drinkard Singers regularly performed at New Hope Baptist Church and later recorded a live album for RCA called A Joyful Noise.

In 1959, she married a Newark City Administrator and entertainment executive John Russell Houston, Jr. She is mother to the late singer and actress Whitney Houston, aunt of Dionne and Dee Dee Warwick and a cousin of Leontyne Price.

Cisco Houston was born Gilbert Vandine Houston in 1918, and died in 1961.

I did not find anything to indicate that Cisco and Cissy were related, but both have very interesting life stories.

-Joe-