need labor legal advice

One of the employees was not formally hired nor he didnt formally apply at a certain company(lets call this business 2). He was actually hired as a part time worker by other business owner(lets call this business 1). But since this business 1 only needs his service just twice or thrice a week, he brought this employee to his brother, the owner of business 2, as extra employee, if they have no operation. Business 2 allowed him as extra so he could help for his extra income. Mr. employee kept his pay envelop when he worked as extra from business 2 and used this envelop (dated 2002) as proof that he was employed at business 2 since the day he received this pay envelop. Business 2 appealed that he didnt hire Mr. employee, that he only accepted him as a regular employee in the year 2008. Could the pay envelop serve as enough evidence in saying that mr. employee is employed at business 2? what if the regular employees of business 2 testify that mr. employee was not employed there during the years that he was claiming, that he was in fact the employee of business 1 from 2002 to 2006.?

Is the pay envelope also a pay slip? If so he can use this as evidence.
Though IMO, this employee has a weak case. Your lawyer knows what defense he can use against this employee's claim.