Sometimes known as left hand marriage also, is a form of marriage in certain countries in which a person of high rank, as a member of the nobility, marries someone of lower status, with the stipulation that neither the low-ranking spouse nor their children, if any, will have any claim to the titles or entailed property of the high-ranking partner.
Examples / related information from British Monarch
> King Edward VIII of England was wanting to marry Wallis Simpson, who was an American and married twice and the second divorce process was progressing. British Cabinet was agains this marriage as British Monarch is the titular head of Church of England and marriage of someone having this status (twice married and ex spouses alive) is not morally fitting to Church of England. At that time, King Edward VIII suggested Morganatic Marriage where in post marriage Wallis Simpson won’t het title of Queen and if they have any kids, they won’t inherit the throne. How ever none of these proposals were appreciated and a situation came if this marriage happens, cabinet will resign and something like Monarch’s neutral stand respecting democractically elected cabient will be undemined. King Edward abdicated his throne and chosen his love and his younger brother assume the throne. Current monarch of England, Queen Elizabeth is the daughter of King Edward’s younger brother who got the throne post abdication of King Edward VIII
>Prince Charlse’s marriage to Camilla was also controversial though many regard this as love story of the other extreme. The faced all ups and downs in their relation and got married after 30 plus years of relation. Though their marriage technically did not happen with the conditiosn of morganatic marriage with documentation, still many apprehend whether she take the title of Queen (if ever Prince Charles become the monarch). She is currently holding the title of Duchess of Cornwall to retain Diana as the only princess of wales. Though once Prince Charles indicated the chance of her assuming the title of Queen once, after an uproar in England, the Palace responds by saying that the intended title would be Princess Consort if Charles became monarch of England as as on date no changes to this proposal happened.
Also, marrying to a British Monarch won’t make the spouse as King of Queen by default as the title to be conferred is based on various deliberations