Egyptian law prohibits marriages for anyone under 18 and the decision for Omar, 12, and Gharam, 11, to marry has sparked outrage among activists.
According to Daily Mail, the father told Egypt's Al Watan newspaper there was 'nothing inappropriate' about the couple, adding that it was only 'an engagement, not a marriage'.
The wedding of the older brother was held 75 miles north of Cairo, and when the announcement was made, guests didn't bat an eyelid, according to the Washington Post.
But photos of the young couple were published in local media which were met with anger.
Reda Eldanbouki, the head of the Women's Center for Legal Aid and Counseling, reported the incident to government agency the National Center for Childhood and Motherhood.
He also filed a complaint with the attorney general to investigate the incident and hold the parents accountable for this 'crime,'
Omar's father brushed off any criticism, and said he 'is a free man and did nothing wrong'.
'Omar has always loved Gharam so much that he used to say he will marry her when they grow up before any other man asks for her hand in marriage when she is older,' he added.'They will get married when they reach the legal age.'He said both children acted 'beyond their years' and had 'strong feelings for each other' through Facebook and other social media and 'wanted to get engaged'