Is this what your were thinking of:
798.34 (d) A senior homeowner who resides in a mobilehome park that has
implemented rules or regulations limiting residency based on age
requirements for housing for older persons, pursuant to Section
798.76, may share his or her mobilehome with any person over 18 years
of age if this person is a parent, sibling, child, or grandchild of
the senior homeowner and requires live-in health care, live-in
supportive care, or supervision pursuant to a written treatment plan
prepared by a physician and surgeon. Management may not charge a fee
for this person. Any agreement between the senior homeowner and
this person shall not change the terms and conditions of the rental
agreement between management and the senior homeowner. Unless
otherwise agreed upon, park management shall not be required to
manage, supervise, or provide for this person's care during his or
her stay in the mobilehome park. This person shall have no rights of
tenancy in the park, but shall comply with the rules and regulations
of the mobilehome park. A violation of the mobilehome park rules
and regulations by this person shall be deemed a violation of the
rules and regulations by the homeowner pursuant to subdivision (d) of
Section 798.56. As used in this subdivision, "senior homeowner"
means a homeowner who is 55 years of age or older.
Sorry, but it doesn't allow you to have what you want.
Custody isn't enough, even if you have that.