now rc....take another angle....what if it was your younger brother having to train you? that's one of my situations...the 5 year old can play better than the 10 year old...but the 5 year old also reads better, is better in math, etc..5 year old is gifted.... so the 10 year old feels dumb compared to her sister 5 years younger..
I am not entirely sure that your case is possible Jay. 5 year olds generally (pardon my sarcasm) are less developed than ten year olds for one primary reason. Puberty. Puberty causes a mass increase in brain growth, so unless the 10 year old has experienced at least some portion of it, there is a very unlikely chance that a 5 year old is better than the 10 year old, especially at subjects such as mathematics, which require developed parietal lobes which are much more developed in a 10 year old than the aforementioned 5 year old. Fingers and movement is also much more developed in the older one. Pardon me if yours is a hypothetical case, but the age difference is just too great. My other hypothesis would be that the 10 year old just doesn't care about anything, hence not progressing and seems "dumb". Motivation is a great role. Also, household circumstance and parental approach is a crucial role in development of any skill, so you might want to take that into consideration.Best.