40 Home Run teammates in a season: three 4 times, two 28 times.

In no season did multiple teams have 3 players hit at least 40 Home Runs (HR).

Seasons with multiple teams with 2 teammates hitting at least 40 HR:
three teams:
1961: Yankees, Tigers, Giants
2015: Angels, Blue Jays, Rockies
two teams:
1999: Mariners, Blue Jays
2000: Astros, Blue Jays
2004: Red Sox, Cardinals

Same two teammates multiple times:
Yankees Ruth, Gehrig: 1927, 1930, 1931 (only teammates tied for league lead: 46 each)
Mariners Griffey, Buhner: 1996, 1997
Mariners Griffey, Rodriguez: 1998, 1999
Rangers Palmeiro, Rodriguez: 2001, 2002

Rockies Castilla, Galarraga: 1996, 1997 in threesomes with Burks and Walker

NYY 4
SEA 4
TOR 4
COL 3 (two: 3 players)
BOS 3
ATL 2 (both: 3 players)
BRO 2
CIN 2
TEX 2

1: DET, SFG, HOU, STL, CHW, LAA

https://stathead.com/tiny/Ufb6S

Rk	Team	Season	Count	Player List
1	ATL	1973	3	Henry Aaron, Darrell Evans, Davey Johnson
2	COL	1996	3	Ellis Burks, Vinny Castilla, Andrés Galarraga
3	COL	1997	3	Vinny Castilla, Andrés Galarraga, Larry Walker
4	ATL	2023	3	Ronald Acuña Jr., Matt Olson, Marcell Ozuna
5	NYY	1927	2	Lou Gehrig, Babe Ruth
6	NYY	1930	2	Lou Gehrig, Babe Ruth
7	NYY	1931	2	Lou Gehrig, Babe Ruth
8	BRO	1953	2	Roy Campanella, Duke Snider
9	BRO	1954	2	Gil Hodges, Duke Snider
10	CIN	1955	2	Ted Kluszewski, Wally Post
11	NYY	1961	2	Mickey Mantle, Roger Maris
12	SFG	1961	2	Orlando Cepeda, Willie Mays
13	DET	1961	2	Norm Cash, Rocky Colavito
14	BOS	1969	2	Rico Petrocelli, Carl Yastrzemski
15	CIN	1970	2	Johnny Bench, Tony Pérez
16	SEA	1996	2	Jay Buhner, Ken Griffey Jr.
17	SEA	1997	2	Jay Buhner, Ken Griffey Jr.
18	SEA	1998	2	Ken Griffey Jr., Álex Rodríguez
19	SEA	1999	2	Ken Griffey Jr., Álex Rodríguez
20	TOR	1999	2	Carlos Delgado, Shawn Green
Rk	Team	Season	Count	Player List
21	TOR	2000	2	Tony Batista, Carlos Delgado
22	HOU	2000	2	Jeff Bagwell, Richard Hidalgo
23	TEX	2001	2	Rafael Palmeiro, Álex Rodríguez
24	TEX	2002	2	Rafael Palmeiro, Álex Rodríguez
25	BOS	2004	2	David Ortiz, Manny Ramírez
26	STL	2004	2	Jim Edmonds, Albert Pujols
27	BOS	2005	2	David Ortiz, Manny Ramírez
28	CHW	2006	2	Jermaine Dye, Jim Thome
29	LAA	2015	2	Albert Pujols, Mike Trout
30	TOR	2015	2	José Bautista, Josh Donaldson
31	COL	2015	2	Nolan Arenado, Carlos González
32	TOR	2021	2	Vladimir Guerrero Jr., Marcus Semien

Those 1973 Atlanta Braves: was there something in the water? Tuesday, August 31, 2010

Home Run Proficiency: Aaron, Johnson, Evans 1973. Wednesday, January 2, 2013

Mantle & Maris still only teammates to hit 50 HR. Tuesday, June 28, 2011

90 Home Runs by two teammates. (Updated 10/6/2023) Saturday, August 17, 2019

Four pairs of teammates hit at least 45 home runs in the same season. One pair did it twice. Thursday, March 22, 2018

***   The End   ***