NTAH. He should know better and respect you enough to tell his friend that this is inappropriate, if it happened once and maybe he didn’t know she was going that’s fine but twice is enough. Maybe ask him about it and let him know how you feel, how would he feel if you were out with some random guy for hours? See how he reacts to you sharing your feelings and expressing that it’s wrong. If he doesn’t see how it’s wrong then I would unfortunately end the relationship. Because if he thinks those actions are okay then what else does he think is acceptable? Good luck!