If the visa you applied is 1 month only and not family visa, i don't think it's extendable. you can only get the Family visit if you apply for the family visit. My suggestion, apply for a family visit visa before their visa expire, then get them to exit Bahrain and come back with the family visa which is good for 6 months.

It's not because things are difficult that we don't dare, it's because we don't dare that makes things difficult!