Who can fast in Ramadan? What are the conditions to be obliged to fast?
One needs to be Muslim, sane, and have reached puberty in order to be deemed accountable in Islam. These criteria are also the conditions for being accountable for fasting. Therefore, in order for an individual to be accountable for the Ramadan fasting, they need to be Muslim, sane, and have reached puberty. (Kasani, Bada’i, II, 87).
Although some people have the qualities to be accountable for acts of worship, they are permitted not to fast due to certain circumstances. (For more information, see Fatwa No. 518 and 520)
Although children who have not reached puberty yet are not accountable for worships, they may be encouraged to perform prayer and fast so that they may get accustomed to them. In this respect, the Prophet Muhammad (saw) recommended that children from seven years of age until ten be made accustomed to performing prayer (Abu Dawud, Salat, 26).
Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS