The rules for including someone in number in college are as follows:
The student is always included.
Other members of the household, except the parents, may be included if they are or will be enrolled at least half time in a program that leads to a college degree, certificate, or recognized education credential at a Title IV institution and for whom the family may reasonably be expected to contribute to their postsecondary education. (West Point and other service academies do not count as Title IV institutions, so siblings who are attending a service academy are not included in the number in college.)