My parents are first cousins and my sister has a learning issue. could i have the gene in me?

Gene defects: For each gene in your body, you have 2 copies; one came from mom and one from dad. So, you have only a 25% chance of having the same gene combination as your sister. Sometimes the gene from one parent controls both genes (a dominant gene) sometimes two rececessive genes must be present to be functional. Consquently, siblings are not very genetically alike unless they are identical twins.