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You would be able to include your brother and sister in your household for determination of whether or not you qualify for food stamps and medicaid.
Here is a link to info on Food Stamps in Texas. There is even a benefits calculator to help you estimate if you qualify and/or an estimate of how much you should expect to receive in food stamps.
You can apply for benefits here: https://www.yourtexasbenefits.com/ssp/SSPHome/ssphome.jsp