so hey listen, your status isn't switched yet. And although your work visa is issued, since iut's not stamped into your passport, you are technically still under your brother's family visit visa.
1. Make sure your family visa is still valid, to avoid penalty
2. Make sure you are not under Work visa yet (check with the immigration office, just go there and ask them! have your passport with you and copy of your family visa)
3. Do not give your passport to the company, otherwise they will switch your visa status to Work visa
4. Once you make sure you are still under family visa, keep looking for the job. Your work wisa will be expired in 3 months from the date of issue, and once you found a new job, the new company can obtain a new work visa for you upon expiry of your current work visa.