Yes they arem they are distant cousing. At least before the bankruptcy money handed to them for their private jets.
Here is the old structure of GM in 2004, when their acquicitions were recently finalized (the brands appeared in a commercial under the banner, there were 7 or 8, Oldsmobile is included it dropped off in 2004 the ads stopped running in 2002 or 2003, i think 2002
1) Chevrolet
2) GMC
3) Oldsmobile
4) Pontiac
5) Buick <----- There were the 'Original 5.'
Now, for the Extended family:
6) Saturn (GM either created it or bought it, but it is GM)
7) Saab (GM wants to sell or kill it now, i dont think it will happen but... OK. Just kill the 9-7X, it is the 5th Trailblazer GMC has made - Trailblazer = 1, Envoy = 2, Olds Bravada was one as well so thats 3, Buick Rainier was 4, and the Saab 9-7X is 5. Oh, and the Isuzu Ascender was 6. Did I miss one? -6-! And they gave GM 17 Billion, and they are getting slipped $26 Billion more for saying they are gonna discontinue the ZR1 most powerful Corvette. They sold them all already. At a premium. Manipulators.)
8) Hummer. (GM wants to kill them too. I like Hummer.)
So that is 8 GM Brands. The 9-2S with Saab shared a platform of Subaru WRX. It lasted 2 years and is a 'Pretty WRX,' Saab has lost its way. Saturn is just a mirror of Chevrolet and Toyota now (the Aura is a cross between Camry and Impala, people.)
And the ... oh wow...
9) Cadillac. Sorry folks.
Lol! the Cadillac Catera was a rebadged Saturn. Wow.
L300 was a limited edition, most were L200s.
I could list family tree of all companies, but there it is. GM will try to sell Saab and fail because who wants to buy them, Saturn should go they are GMs new Oldsmobile, the Ion has a Honda engine, sucked beyond bad its first two years, and generally is failing to attract buzz beyond the Sky, which should remain as a Chevrolet if I was GM. Hummer may go the way of dinosaur, but they should keep itm just waay scaled back. GM are idiots.
It should also be noted that GM bought Isuzu (Rodeo? remember? Trooper = Bad.. Axiom = Weird... VehiCROSS = weird and specialty. Not caught on. They made car sin the early 90s and had the Amigo as the Chevy/Geo Tracker.) -- Isuzu has been quietly discontinued bascially at most recent 2 years ago, but officially this year. No more Isuzu, they were dead in the water since they stopped making Rodeo, which was decent SUV until it became cheapened.
Geo also got sucked into Chevy and GM. Look at any Geo, the Chevy cross is in the middle.
I hope this helped, and shamelessly ask for Best Answer if it did.