If I was 7 when my sister was 16 and my brother was 8 when she is 19 how many more years will it take my brother to reach 21 when I'm 13?

Let us suppose my brother was born March 2, 1990, my sister was born March 3, 1978, and I was born March 4, 1986. On March 3, 1994, my sister is 16 and I am yet 7. On March 2, 1998, my brother is 8 and my sister is still 19. On my thirteenth birthday in 1999, my brother is only 9, and it will be almost 12 more years before he reaches age 21.

Now let us suppose my twin brother and I were born in 1990.  Being older, I was born March 1 and my brother, a late delivery, was born March 2. If I had been born shortly before midnight and my brother shortly after, it is possible to have been born only minutes apart. Our older sister shares the same bithday of my brother, but was born in 1980.  On my seventh birthday in 1997, my sister is still 16.  On my brother's ninth birthday, my sister is not yet 20, but 19.  When I am 13, my twin is nearly 13, too. Thus it will only be about  8 more years before he and I reach age 21. 

Of course, ignoring fractions of a year, it will be 10 more years before my brother is age 21. 

Edited on July 6, 2006, 4:01 pm

Posted by Dej Mar on 2006-07-03 14:43:24