Fathwa, - How old does a son have to be to be a mehram

Question:
I want to now how old does my son have to be before i can travel with
him as my mehram. e.g for hajj?
Answer:
wa`alaykum as-salam wa-rahmatullah
All praise is to Allah. Blessings and peace be upon the Messengerof Allah.
The mahram with whom a woman travels should be
1) Adult (baligh) by the definition of the shari`ah, (or at least
nearadult [Durr al-Mukhtar]).
(Adulthood for these purposes is defined as the first period for a
girl, or the first wet-dream for a boy, or 15 lunar years of age for
both as aprecautionary upper limit.)
2) Sane
3) Upright, trustworthy and responsible
There is not a specific age which can be used universally; rather what
is important is that the mahram (the son, in yourcase) fulfills the
conditions mentioned above. The rationale is that the mahram should be
capable of protecting the woman and her honor. Clearly a minor child
and an insane person cannot even take care of themselves, let alone
watch out for someone else. nor can anirresponsible or morally corrupt
person be expected to fulfill this role.
[References:
- Radd al-Muhtar, Ibn `Abidin, 3/464 (Dar al-Kutub
al-`Ilmiyyah)
- al-Mughni, Ibn Qudamah, 3/193-4]
And Allah knows best.