undertaking medically approved care of a person is covered under the 52 weeks rules – so as long as you are happy the care/support he is providing is medically approvied, then hes fine
(16) This paragraph shall apply to a person who is temporarily absent from the dwelling he normally occupies as his home (“absence”), if—
(a)he intends to return to occupy the dwelling as his home; and
(b)while the part of the dwelling which is normally occupied by him has not been let, or as the case may be, sublet; and
(c)he is—
(v)undertaking medically approved care of a person residing in the United Kingdom or elsewhere;
