Yvette younger brother just turned 3 years old. Fred brother is now 30 months old who's brother is older

You can convert 3 years into months

there are 12 months in one year

so 3 years would be (3*12) months

which would be 36 months

then compare 36 months to 30 months

which is bigger?

36 months

therefore Yvette's younger brother is older.

3 years is 12 months x 3 which is 36 months

Therefore Yvette bother is older because he is 36 months which is 3 years