Visit visa for indians in sinagpore

In my previous comment to you, I had mentioned very clearly that before you post your further questions, please read old posts.

I think you didn’t do your homework. This question was replied many times.

Your employer is correct, less than 6k per month salary, you are not allowed to bring your family on DP.

On visit visa, a person can stay 30 days (but check white embarkation paper to see if it is given lesser). It can be extended one more month. Max is 90 days but that’s only possible in the case of medical treatment or any other serious illness issues.

Most of the information you are asking for is available by a simple Google search or some reading on this forum.
Your family members can apply for a tourist visa (SVP) at your country's Singapore embassy. It is usually granted for 30 days (sometimes only 15 days). After arrival, they can apply for an extension up to 89 days at ICA - but they need a good reason for wanting to stay that long. I am not sure if visiting family members is a good reason, as it might be seen as circumvention of the dependents pass (DP) rules - and Singapore authorities really dislike any attempt at circuimventing their rules.
After return to their home country, there is no clear rule when they can apply for the next SVP, but it is probably advisable to wait at least as long as they were in Singapore before.