Haplogroup G in Europe: Celtic or Sarmatian?

[Bosniensis]

Here are some famous G gangsters. They claim Otzi is actually the oldest european genome ever tested.

Larry Bird (photo by Steve Lipofsky - CC BY-SA 3.0)
Larry Bird (b. 1956), an American professional basketball executive, former coach and former player for the Boston Celtics, is thought to belong to haplogroup G-Z6748 (downstream of Z1816 and Y8903) based on the testing of several relatives descending from Thomas Bird at the Haplogroup G-L497 Y-DNA Project. Larry Bird is the only person in NBA history to be named Most Valuable Player, Coach of the Year, and Executive of the Year.

So if Larry Bird is G and he played for Boston Celtics

Then obviously G is Celtic.

[Rethel]

Is it related to Celtic tribes or Sarmatian groups like Alans? Or none of them?

Oldeuropean.