Should one use the past or the present tense when asking about age?
A:There was once my nephew told me many times that he loves me.
B: How old was he/ How old is he?
Not a teacher.
Generally you use past tense when the person is dead, and present tense if the person is still alive. If you use the present tense because you don't know that the person is dead, then the person answering will say their age in the past tense. The age in the past tense refers to how old the person was when they died.
Real life example:
I am 21 years old. My grandpa was 64 years old. I am still alive while my grandpa is not.