what are the requirements for the visiting visa?

I think he needs to apply for the S2 type one. Its longest duration for each stay is 180 days. The required documents are:
1.Passport: it should be valid more than six months and have more than two blank pages. The original and copy of the info page are needed.
2.Filled application form and remember to put the recent personal passport size photo on it.
3.Guarantee letter from your employer and the business license of your company
4.Recent six months savings: 5 million shillings
5.Invitation letter from his brother
6.Kinship certificate.