Answer:
We only use “po” and “opo” for our parents and other older people, except our siblings.
We use “kuya” for any older brother and “ate” for any older sister.
Traditionally, we used to have more according to birth order:
Kuya/ate = 1st child (boy/girl)
Diko/ditse = 2nd child
Sangko/sanse = 3rd child
Siko/sitse = 4th child
Bunso = youngest child, regardless of gender
These are very rarely used nowadays.