For a dependant relative (eg father, mother) to enter the UK and stay for more than six months they will require a Family of a Settled Person Visa. A Standard Visitor Visa (LINK TO PAGE 14) is fine if you want to stay for less than six months.
To apply for a Family of a Settled Person your dependant relative must have a family member living permanently in the UK who is either a British Citizen, has settled in the UK, or who has asylum or humanitarian protection in the UK. It usually takes about 12 weeks to get a decision and they may have to pay the health surcharge (which entitles them to medical treatment from the National Health Service). With a Family of a Settled Person Visa they can work in the UK. They may be able to extend their visa and settle in the UK permanently (Indefinite Leave to Remain).
If you apply through MyUKVisas, we will help you present the best possible case so you have the highest chance of success.