After this comment you offered to prove them false.
Lol.
What does the Quran say? Please follow this and understand the logical representation of this subject.
1. You can only give inheritance to a mature person.
And do not give the immature ones your money for which God has made you overseers, and spend on them from it and clothe them, and speak to them in goodness. – Quran
4:5
Immaturity is described by the Arabic word Shufaha. Which the child is yet not ready to take up responsibility of managing his or her finances. This is speaking of an orphan under your care but yet it defines when a child can inherit, an age where s/he is mature enough to manage it.
2. So when do you test the child for maturity?
Quran calls it Balaghul Nikaha.
And test the orphans when they reach age of marriage, then, if you have determined from them comprehension/maturity/age of marriage, then give them their money, - Excerpt – Quran
4:6
Maturity, the age of marriage is tied to your ability to manage your own finances and inheritance.
3. Rushdan, in 4:6 means sound judgement. Thus, the age of marriage is also defined by sound judgement.
Thus, there are easily four criteria for the age of marriage.
1. Not Shufaha or immature, childish.
2. Balaghul Nikaha or the age of marriage which is synonymous in classical Arabic to maturity.
3. Sound judgement.
4. Mature enough to inherit their wealth and manage their finances.
What age do you think a girl can fit into this criterion? 9? 12? 19? 20? Think.
Another reference to maturity is full physical growth as in Quran 40:67 where Ashaddakum from the root Shadad means full physical growth. So you must know when your child is full grown.