Hazrat I found this extract from the English translation of Umdat As Salik (Reliance of a Traveller). Even though the minimum age isn't directly mentioned, this might help I hope. (1) The only guardians who may compel their charge to marry are a virgin bride's father or father's father, compel meaning to marry her to a suitable match (def: m4 [look below] ) without her consent. (2) Those who may not compel her are not entitled to marry her to someone unless she accepts and gives her permission. Whenever the bride is a virgin, the father or father's father may marry her to someone without her permission, though it is recommended to ask her permission if she has reached puberty. A virgin's silence is considered as permission. As for the nonvirgin of sound mind, no one may marry her to another after she has reached puberty without her express permission, no matter whether the guardian is the father, father's father, or someone else. m3.15 No guardian may marry a woman to someone who is not a suitable match (def: m4) without her acceptance and the acceptance of all who can be guardians (def: m3.7). If the Islamic magistrate is her guardian, he may not under any circumstances marry her to someone who is not a suitable match for her. If the bride selects a suitor who is not a suitable match for her, the guardian is not obliged to marry her to him. If she selects a suitable match but her guardian chooses a different suitor who is also a suitable match, then the man chosen by the guardian takes precedence if the guardian is one who may lawfully compel her to marry, while the one she selects takes precedence when the guardian may not lawfully compel her to marry. m4.0 A SUITABLE MATCH (KAFA'A) (N: The definition of a suitable match should not be misunderstood as a recommendation for whom to marry. It is merely a legal restriction to protect a woman's interests when the father or grandfather of a virgin marry her to someone without her consent (dis: m3.13,15). As for when she wishes to marry someone who is not a suitable match, and her guardian has no objection, there is nothing wrong or offensive in her doing so.)