Yes, but think carefully. Will this person be there to support you? Or will they disrupt the mediation? Remember they will also be bound by confidentiality.
Make sure to speak with the mediator before the mediation if you are thinking about bringing someone with you. You may need to arrange with the other side who each of you will be bringing. Whoever you bring will need to understand that the mediation is confidential and that they will be just as bound by confidentiality as you are.