The high court had annulled the election of the son of Samajwadi Party MP Mohammad Azam Khan on the grounds of being under age.
Abdullah Azam had furnished the wrong date of birth in his poll affidavit and won as an MLA from Swar Tanga in 2017 when he was not 25 years old.
Khan along with his son, Abdullah Azam, will be taken from the Sitapur jail to appear in the Rampur court for hearings in a forgery case.
Khan, Fatima and Abdullah were sent to seven-day judicial custody in a forgery case after they surrendered in a Rampur court on Wednesday.
Khan's legislator wife Tanzeen Fatima and their son and disqualified MLA Abdullah Azam were also taken to Rampur amidst tight security in connection with a hearing in another case.
The Suar assembly seat in Rampur has been declared as vacant from that date as well, the notification said.
Khan and his family surrendered before a Rampur court on Wednesday and were sent to judicial custody till March 2 over Abdullah's allegedly fake birth certificate.
The Khan family had been ignoring summons by the courts in various cases lodged against them as a result of which warrants were issued against them.