Let's ignore if Guardians as a whole can be used by MCU, but who can be used with the families restriction (solely based on comics)?
Star-Lord is fine. No family ties him.
Drax is out. He was part of Iron Man, Avengers, Fantastic Four, and Thanos stories before being part of Guardians.
Thanos is out. Obviously. Same with The Collector, he's an Avenger villain. Ronan is out too, he was a baddie for Avengers and FF. He also is part of the Kree race, which is involved in all comics.
Here's the tricky ones:
Gamora appeared in a few Avengers comics, and is the daughter of Thanos, so they can make a case she can't be used.
Groot and Rocket Racoon were both part of Hulk comics until they joined the Guardians in the 2000's, but they weren't featured a lot. Groot was actually part of a branch of SHIELD (the "Paranormal Containment Unit" before joining Guardians). Their line isn't as clearly drawn though. They could probably be used, but again.... there is some history there that could make them not accessible.
Star-Lord is fine. No family ties him.
Drax is out. He was part of Iron Man, Avengers, Fantastic Four, and Thanos stories before being part of Guardians.
Thanos is out. Obviously. Same with The Collector, he's an Avenger villain. Ronan is out too, he was a baddie for Avengers and FF. He also is part of the Kree race, which is involved in all comics.
Here's the tricky ones:
Gamora appeared in a few Avengers comics, and is the daughter of Thanos, so they can make a case she can't be used.
Groot and Rocket Racoon were both part of Hulk comics until they joined the Guardians in the 2000's, but they weren't featured a lot. Groot was actually part of a branch of SHIELD (the "Paranormal Containment Unit" before joining Guardians). Their line isn't as clearly drawn though. They could probably be used, but again.... there is some history there that could make them not accessible.