Gary Thain had no, absolutely, relation with Captain Beefheart.
Gary Thain was a brilliant bass player-one of the best I have ever heard- which helped a band like Uriah Heep to touch the top. It wasn't accidently that Thain was in U.H. in their best albums.
Gary Thain before U.H., was in Keef Hartley Band, from their very first album until 72 brave (five studio albums plus on live at the famous Marquee club) . He was also, in the legendary Martha Velez 's "Fiends and Angels" (1969) album , together with musicians like Jimmi Hendrix, Eric Clapton, Paul Kossof, Brian Auger, Jack Bruce and others.
In 1972 he played in 4 albums ,72 Brave of K. Hartley, Miller Anderson 's "Bright City", Demons and Wizards and Magician's Birthday of Uriah Heep. In K. Hartley 's 72 Brave you may listen to the song "You say your together now" which is the only song Thain has sung alone.
In 1974 had an sirious electrocution accident on stage in Dallas U.S. He stayed unconcious for a couple of hours. Then, due to his health problems, couldn't follow U.H. 's concerts ...thus the band fired him (!!!???)...Next year Gary Thain died ( December 1975 and not in 80's )
Uriah Heep hired John Wetton to replace him, for the next two albums, without any luck. They have never managed to make a great album after Gary 's death. Instead of this Byron had alcohol problems and finally died 10 years, later than Gary 's death .
The irony is that Byron died, exactly, as 12 years before his death, he was singing in "stealin'" song of "Sweet Freedom" album..."wine and women gonna put me in an early grave"...In the cover of the same album you may see from left to right, first Gary Thain died in 1975 and next to him David Byron died 10 years later...
Happy Loss