Torres/Sanchez and Ruth/Gehrig: season home runs off one team.

Two pairs of Yankee teammates have hit at least 10 home runs against a team in a season:
Babe Ruth and Lou Gehrig 1927 off Boston Red Sox pitchers
Gleyber Torres and Gary Sanchez 2019 off Baltimore pitchers

Ruth and Gehrig had an epic home run race in 1927, similar to that of Mickey Mantle and Roger Maris in 1961. Ruth and Gehrig were tied at 45 in early September 1927. They finished 60-47. Ruth, who had set the career record for home runs in the 1921 season, set the season record for the fourth and final time in 1927 as he broke his own record for the third time, the first with Yankee Stadium as his home ballpark:
1919 29 HR Fenway Park as a Red Sox
1920 54 HR Polo Grounds as a Yankee
1921 59 HR Polo Grounds as a Yankee
1927 60 HR Yankee Stadium as a Yankee

1927	Opp	G	GS	PA	AB	R	H	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	TB	GDP	HBP	SH	SF	IBB	ROE	BAbip	tOPS+	sOPS+
Ruth	Boston Red Sox	22	22	105	87	31	34	6	0	11	30	2	0	16	13	.391	.485	.839	1.325	73		0	1		0	1	0.365	109	229
Gehrig	Boston Red Sox	22	22	105	89	28	37	8	3	11	35	4	1	14	12	.416	.495	.944	1.439	84		0	0		1	0	0.394	128	256
1927	Opp	G	GS	PA	AB	R	H	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	TB	GDP	HBP	SH	SF	IBB	ROE	BAbip	tOPS+	sOPS+
Ruth	Fenway Park	12	12	59	49	17	20	4	0	8	20	1	0	8	8	.408	.491	.980	1.471	48		0	1		0	0	0.364	128	304
Gehrig	Fenway Park	12	12	59	48	14	20	5	2	6	18	2	1	11	8	.417	.525	.979	1.505	47		0	0		1	0	0.412	139	313
2019	Opp	G	GS	PA	AB	R	H	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	TB	GDP	HBP	SH	SF	IBB	ROE	BAbip	tOPS+	sOPS+
Torres	Baltimore Orioles	18	17	75	66	22	26	4	0	13	20	0	0	9	12	.394	.467	1.045	1.512	69	1	0	0	0	1	0	0.317	234	238
Sanchez	Baltimore Orioles	14	13	61	55	12	20	1	0	10	22	0	0	4	9	.364	.426	.927	1.354	51	0	2	0	0	0	0	0.278	217	203
2019	Opp	G	GS	PA	AB	R	H	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	TB	GDP	HBP	SH	SF	IBB	ROE	BAbip	tOPS+	sOPS+
Torres	Camden Yards	9	8	36	30	12	12	2	0	7	10	0	0	6	6	.400	.500	1.167	1.667	35	1	0	0	0	0	0	0.294	267	286
Sanchez	Camden Yards	7	6	31	28	8	10	0	0	7	16	0	0	1	4	.357	.419	1.107	1.526	31	0	2	0	0	0	0	0.176	249	249

Through the final Orioles game yesterday:
Torres 26 HR, 13 against Orioles
Sanchez 26 HR, 10 against Orioles

Torres and Sanchez had many fewer AB against the Orioles than Ruth and Gehrig had against the Red Sox.

Most career Home Runs by 2 teammates: Ruth+Gehrig, Mathews+Aaron, Mays+McCovey? Tuesday, August 13, 2019

Gleyber Torres could set a Home Run record for most against a team in a season. Monday, June 3, 2019 9:30 AM

Maris hit 13 of 61 against White Sox: 21.3%
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Lou Gehrig: most home runs against a team in a season - 14 Cleveland 1936. Monday, June 3, 2019 4:39 PM