Dilemma between present perfect simple and past simple

I do not know where to find the right answer. Please tell and explain what my errors are

I must use either the Present Perfect Simple or Past Simple

 B. How long / you / have /that?
 A. We / have / it since the kids / be / tiny. It / belong / to my parents before us, so it / be / the family holiday home for a long time.
 B. / you / go / there when you / be / a child?
 A. Yes. Then my father / want / to sell it so I / buy / it.

My version

 B: How long have you had that?
 A: We've had it since the kids were tiny. It's belonged to my parents before us, so it has been the family holiday home for a long time.
 B: Did you go there when you were a child?
 A: Yes. Then my father wanted to sell it so I bought it.

I am not sure about the solution in bold. Should it be “it belonged” or “it's belonged”? Is it OK to use the Present Perfect and Past Simple together in the same sentence?