In case of proprietorship of two firms of one owner then such financial statements of the firms should be prepared in consolidated basis and itr should be filled.
Partnership income should also be included in return
Mr. X is an Individual who have 3 sources of Income. You need to file just 1 ITR showing income from all the 3 sources. Proprietorship Income will be taxable whearas Income from Partnership is not taxable as taxes are to be paid by the firm.