When I was 6 years old, my sister was half of my age and my brother was twice of my age. 5 years later, what is the sum of the siblings' ages?

The Sum of all the siblings ages are 36.

Explanation:

Your sister was half your age (3).

Your brother was twice your age (12).

It says 5 years later ...

so then your sister is 8

brother is 17

your 11.

When you add all of these ages up you get the answer 36.