Question

Which sentence contains parallel structure? Derrick’s sister was proud that her big brother coached her soccer team. Derrick coached his sister’s soccer team and managed his brother’s baseball team. Derrick had managed his brother’s baseball team for the past three seasons. Derrick was a great older brother, helping to coach his siblings’ sports teams each season.

Answer 1

I would say that the sentence which contains parallel structure is the second one - Derrick coached his sister's soccer team and managed his brother's baseball team.
The same tense is used in both verbs (coached and managed are both in past simple tense).

Answer 2

The correct answer is - Derrick coached his sister’s soccer team and managed his brother’s baseball team. 

A parallel structure means that the same form of a word is used throughout the sentence. As you can see in the sentence above, the same form of the verbs is used - both verbs are used in the past tense (coached and managed). The other options have varying forms, and therefore are not parallel.