He can file a single tax return to report his income. He is not required to file a return with less than $6300 of W-2 income. If his income was reported on a 1099-MISC or no form, he must file a return if it was over $400 to pay self employment taxes.
If he files a return AND he meets the tests to be claimed by you, he must indicate on his return that he can be claimed by someone else.
