No, your kitchen appliances do not need to be the same brand — you should buy the appliances that functionally work best for you.
However, for aesthetics and resale value, it’s usually best to have all your appliances be the same color or finish. Each brand will have slight variations in their finishes, so two black or stainless steel appliances may be slightly different in color or sheen. If you’re a perfectionist, consider sticking to the same brand.