Final answer:
The name of the third child is Timmy, as stated at the beginning of the riddle.
Step-by-step explanation:
The question posed is a play on words and requires careful reading to answer correctly. Timmy's mother had three children. The first child was named April, the second was named May. The prompt already mentions the name of the third child at the very beginning - the third child's name is Timmy. It's a common riddle that aims to catch the reader off-guard by assuming a pattern (months of the year) that is not relevant to the answer. Instead, the information given at the very start holds the key to the answer.