Sponsoring a lost child

The orphan is a child whose father has died, as was
stated by the scholars in Lisaan al-‘Arab [an Arabic-language dictionary] and
elsewhere. Such a child is regarded as an orphan until he reaches the age of puberty,
i.e., the age of fifteen or earlier if the signs of puberty appear. These signs are: the
emission of gushing water (ejaculation) during intercourse or a wet-dream, the growth of
coarse hair around the private parts, and, in the case of females, the onset of
menstruation.

(See Al-Mughni by Ibn Qudaamah, 6/591)

As for the child whose father is missing, he is not
considered to be an orphan unless it is proven that his father is dead, or a period of
time passes beyond which it is impossible that his father would still be alive; this
should be left to the discretion of the judge, as stated by the majority of the fuqaha’
on the topic of the inheritance of one who is missing.

If this child is poor or comes from a poor family, then money can be
spent on him from the Zakaah or general charity funds, but orphan sponsorship does not
apply in his case.