Want to come on visitor visa once to check employer before joining.

There are a certain no of ways to get a tourist visa in Oman

1. You have to have a passport from a country that can avail on arrival visa in Oman :http://www.rop.gov.om/english/countrylist1.asp

2. You can get a family visa (only if you have a blood relative), your own brother etc.

3. Else, you can enquire on a tourist company to arrange for a visa, most often than not, you have to use their tourist package.

4. You can also ask an Omani National / Company to sponsor you for a visa.

but as i read on visa laws it stats that if i have a relative (not only blood relation but like cousin, uncle etc) i can apply for family/ relative visit visa.

http://www.rop.gov.om/english/dg_pr_vis … evisit.asp

so, if i avail this above mentioned visa, for  how long i cant come to oman after returning from oman? as i want to return oman on work visa.

Yes but that relative visa is essentially sponsored by your relative's employer..... which boils down to the fact that it is being sponsored by an Omani National. (Which is my fourth point)

Your relative on his own, CANNOT make an application for a tourist visa or any kind of visa, you need it to be approved by an Omani National.