It is narrated from Sayyiduna Ali (may Allah be pleased with him) that he said: There is no marriage without a guardian; whoever marries, or gives in marriage, without a guardian, his marriage is void.
It is narrated from Sayyiduna Ali (may Allah be pleased with him) that he permitted the maternal uncle and the mother to give in marriage (acting as guardian).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13646