No, depending upon the situation. One key requirement to claim a dependent is that you must provide more than 50% of their support, which is the cost of basic life necessities.
To determine this, compare how much you spend on this person's necessities with how much they (or somebody else) contributes.
If you are paying more than 50% of another person's necessary living expenses, you financially support that person.
For other dependent requirements review FAQ below: