Junior Groomsman

I really would like for my nephew to be in our wedding, but at 10 years old he is too old to be a ring bearer. Therefore, i want him to be a junior groomsmen, but do not really have anyone to be a junior bridesmaid with him. Would it be strange to only have him by himself or are there other ideas for ways for him to participate?

Also, i have heard mixed explanations on what a junior groomsman and junior bridesmaind actually are. Some say it is only for sons or daughters of the bride or groom.