I was in my best friends wedding many years ago now and she had three bridesmaids but her DH had just two groomsmen. The matron of honour and the best man were together in most photos while me and the other bridesmaid shared the groomsman, if that makes sense. When it came to the bridal waltz, I danced with the brides brother as I'd known him for years and he was all suited up so he looked the part.

It worked fine! Good luck!