Even worse, say the parents, they do not want to marry until they are 19 or 20.
In Africa, many girls still do not attend school, because their parents are afraid of them meeting people who might drive them from their traditions.
They are afraid that educated girls will argue with them, and want more control over their lives.
Even worse, say the parents, they do not want to marry until they are 19 or 20.
A young girl often does not have a say in whether and whom she will marry. It is the parents, both the man's and the girl's, who make the decision.
The girl is frequently subordinate to her older partner in big family decisions, such as when to have children and how many to have.
Many of these girls, in villages and towns throughout sub-Sahara Africa, are only about 12-years-old. But such marriages are common, even though early unions have been illegal for decades in a number of African countries.
Domestic violence
The grandmothers who lead the wedding ceremonies repeat with oppressive voices for many months: "You should obey him, no matter what!"
If they go to their relatives, they are told it is their own fault. And when a young girl goes to the police it is dismissed as "a family problem".
Parents think to themselves: "We live in a period when girls chase boys, have sex, produce babies, earn reputations, and shame families. The communities will not respect them and people will say we failed to fulfil our duties as parents."
They believe that if a girl does not marry at an early age, she will sleep with many men, and nobody will want to marry her later. Marriage is a way of keeping girls from sexual adventures, they argue. It also strengthens clan relationships and honours their traditions, say African communities.
Polygamy
Last century our grandfathers picked wives who were as young as eight. My grandmother told me she saw my grandad at her father's house a lot when she was very young. He never brought gifts for her, never joked with her, seemed to barely see her.
And no-one told her that he had picked her to be his bride.
The world "paedophile" does not exist in any African language.
The practice of forcing a girl into marriage took hold centuries ago throughout sub-Sahara Africa, but it continues to be widespread, especially in countries with large Muslim populations. The marriage typically takes place within clans with polygamous traditions.
The girls are forced to wed distant relatives who are often three or four times their age and who sometimes have chosen the girl long before puberty.
When a teenage girl gets married in Africa, her husband's status is seen as being just under God. Forced marriages have increased in the last decade, when poverty and economic conditions got worse - families often receive hundreds, even thousands of dollars as marriage dowry.
Men think virgins will reduce the chances of them bringing HIV/Aids to the big polygamous family. Teenage marriages are also common in conflict situations - girls have served as concubines in military basis in Angola, Sudan and the Democratic Republic of Congo.
Shortly after their wedding, or co-habitation, the girls spend days doing housework, preparing meals, washing clothes, and scrubbing pots and plates.
Health risks
Analysts on Islamic law say the Koran does teach that a girl can be married as soon as she can conceive, but they say the religion does not condone forcing girls into wedlock.
Medical professionals say pre-adolescence marriage is partly responsible for Africa's maternal mortality rates, one of the highest in the world.
It is not unusual for both mother and child to die during the birth. Early marriage is closely linked to early, repeated and unplanned childbearing. Death rates are also higher for both mothers and babies, as teenage bodies are not ready for rigours of pregnancy or childbirth.
Data from 22 sub-Saharan African countries shows the highest rates of teenage girls either married or cohabiting are in Mali, Niger, Uganda, Burkina Faso and Cameroon.
In 14 of the countries studied, more than 25% of girls in this age group are married or cohabiting. Five countries have rates above 40%.
The data includes marriage, forms of cohabitation and polygamy.