The words genes, jeans sound the same but have different meanings and spellings. Why do genes, jeans sound the same even though they are completely different words?
The answer is simple: genes, jeans are homophones of the English language.
Plural form of gene.
A patronymic surname derived from a medieval variant of John.
Plural form of Jean.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.