Yeah, it looks like for the sake of the 18-21 year old receiving a handgun, the transfer can only be between a parent and child or between grandparent and grandchild.
Edit: ONLY a parent or grandparent?
(c) (1) Subdivision (d) of Section 12072 shall not apply to the
infrequent transfer of a firearm that is not a handgun by gift,
bequest, intestate succession, or other means by one individual to
another if both individuals are members of the same immediate family.
(2) Subdivision (d) of Section 12072 shall not apply to the
infrequent transfer of a handgun by gift, bequest, intestate
succession, or other means by one individual to another if both
individuals are members of the same immediate family and all of the
following conditions are met:
(A) The person to whom the firearm is transferred shall, within 30
days of taking possession of the firearm, forward by prepaid mail or
deliver in person to the Department of Justice, a report that
includes information concerning the individual taking possession of
the firearm, how title was obtained and from whom, and a description
of the firearm in question. The report forms that individuals
complete pursuant to this paragraph shall be provided to them by the
Department of Justice.
(B) The person taking title to the firearm shall first obtain a
handgun safety certificate.
(C) The person receiving the firearm is 18 years of age or older.
(3) As used in this subdivision, "immediate family member" means
any one of the following relationships:
(A) Parent and child.
(B) Grandparent and grandchild.