If i am 16 can i claim my you ger sibling as a dependent my mother is unemployed and i have been providing the things he needs

Probably, if you your mother doesn't have to file a tax return.

.A child closely related (sibling counts) to a taxpayer can be a “Qualifying Child (QC)” dependent, regardless of the child's income, if:

1.              He is under age 19, or under 24 if a full time student for at least 5 months of the year, or  is totally & permanently disabled

2.              He did not provide more than 1/2 his own support

3.              He lived with the relative (including temporary absences) for more than half the year

4.              He is younger than the relative (not applicable for a disabled child)

5.              If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child (this essentially means that you have the parent’s permission to claim the child, if the child also lived with the parent more than half the year)

6.              If the parents of a child can claim the child as a qualifying child but no parent so claims the child, no one else can claim the child as a qualifying child unless that person's adjusted gross income (AGI) is higher than the highest AGI of any of the child's parents who can claim the child.

https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Return/INF12139.html

There's one additional rule: a dependent cannot have a dependent of his own. So, if your mother is required to file a tax return (e.g. her unemployment compensation is high enough to require her to file), you can not claim any dependents because you qualify as her dependent (even if she doesn't actually claim you).