Please see the immigration rules here:
http://www.ukba.homeoffice.gov.uk/polic ... sandother/
317. The requirements to be met by a person seeking indefinite leave to enter or remain in the United Kingdom as the parent, grandparent or other dependent relative of a person present and settled in the United Kingdom are that the person:
(i) is related to a person present and settled in the United Kingdom in one of the following ways:
(a) mother or grandmother who is a widow aged 65 years or over; or
(b) father or grandfather who is a widower aged 65 years or over; or
(c) parents or grandparents travelling together of whom at least one is aged 65 or over; or
(d) a parent or grandparent aged 65 or over who has entered into a second relationship of marriage or civil partnership but cannot look to the spouse, civil partner or children of that second relationship for financial support; and where the person settled in the United Kingdom is able and willing to maintain the parent or grandparent and any spouse or civil partner or child of the second relationship who would be admissible as a dependant; or
(e) parent or grandparent under the age of 65 if living alone outside the United Kingdom in the most exceptional compassionate circumstances and mainly dependent financially on relatives settled in the United Kingdom; or
It is very hard for parents to join their children in the UK if one of them is not 65 or over. It is not straightforward if over 65 either.
They may have to just visit.
