Answer:
My uncle's ambition was to retire and to live a life of leisure.
Step-by-step explanation:
In grammar, parallelism (also referred to as parallel structure and parallel construction) is the use of the same or similar grammatical structure within phrases, clauses, or sentences.
Parallelism is present in the underlined part of the given sentence: My uncle's ambition was to retire and to live a life of leisure. The grammatical structure that is repeated twice is the infinitive - the basic form of a verb. The infinitive can be used with or without the infinitive marker to. Here, it's used with to both times, although it could've been omitted before live. This is why this is an example of parallelism.