It seems that with changing times even the British royalty’s perception of marriage has undergone a change.
Forms for Buckingham Palace's royal garden parties specifically mention that the Peers’ kids living with partners will be considered married. A notation in the form clearly states: "NB living with partner = married."
The forms, entitled Her Majesty's Garden Parties 2007, specify that members of the House of Lords may bring up to two unmarried sons or daughters between the ages of 18 and 25 to the Buckingham Palace party.
Children co-habiting with their partners will be considered married, and cannot come.
Buckingham Palace declined to comment on the ruling. But MPs say the decision to consider co-habitees on the same terms as married people showed the palace was more in touch with how people live than many might think.
Lorely Burt, equalities spokesman for the Liberal Democrats, said: "I am glad the palace is up to date with how people live in Britain today."