If I were to sit down right now, bust out my dick and start jerking off while my female friend sat near me or in the same room and started fingering herself at the same time, you damn well better believe I consider that cheating if I didn't tell/ask/get permission from my partner. And I would be hard-pressed to find people in the real world who would think otherwise, either.
The fact that you are both the same gender doesn't change anything, gender has nothing to do with it. Both of you being men does not make it less serious. That said, if you have your partner's blessing than it absolutely is not cheating and 100% acceptable. Anything sexual/intimate that involves another person should always be a decision made by both in the relationship beforehand, imo.
This is not a gendered issue, this is a trust and consent issue.
The fact that you are both the same gender doesn't change anything, gender has nothing to do with it. Both of you being men does not make it less serious. That said, if you have your partner's blessing than it absolutely is not cheating and 100% acceptable. Anything sexual/intimate that involves another person should always be a decision made by both in the relationship beforehand, imo.
This is not a gendered issue, this is a trust and consent issue.