Prince William, Harry's children can't marry without consent of King Charles?

The first six people in the line of succession to the British throne cannot marry without the consent of the reigning monarch as per the royal marriage law of 1772 and the Succession to the Crown Act 2013.

During King Charles III's reign, Prince William's all three children and Harry's eldest child have to take permission from the monarch if they come to a certain age of marriage in his reign.

William, who's married to Kate Middleton, is now the first in line to the throne as the eldest son of King Charles III, the reigning monarch.. 

Kate Middleton and William's eldest son Prince George is second in line to the throne, after his father. While, Princess Charlotte is third in line to the throne, after her father and older brother.

Prince Harry, who's married to Meghan Markle, is fifth in line to the throne. However, the couple's first child, Archie Harrison Mountbatten-Windsor is sixth in the line.

It means that before finding their life partners William's three children and Harry's eldest son Prince Archie will have take permission from King Charles if they come to a certain age and decided to marry during his reign.

However, Meghan and Harry's daughter Princess Lilibet, who is seventh as per current line of succession, is out of this restriction or rule. 

King Charles III's younger son Prince Harry opened up about being oblivious to the rules surrounding royal engagements, which saw him require permission from his late grandmother Queen Elizabeth II before he popped the question to former actress Meghan in 2017.

Harry did not realise these were serious rules that must be followed, he admitted in his new book Spare – although he recalls his father King Charles asking permission to marry Camilla, he did not remember Prince William needing to do the same when he proposed to Princess Kate.

So, after admitting he was ready to ask for Meghan's hand in marriage, he had to bring it up in conversation with the Queen – a task he said filled him with fear.

Princess Margaret reportedly was prevented from marrying divorcee Captain Peter Townsend, while the Duke of Windsor even abdicated the throne in order to remain with American socialite Wallis Simpson, who had been divorced twice before.

Former Hollywood star Meghan was previously married to Trevor Engleson, so it's likely that Harry feared that history would repeat itself.

After the ascension of Prince William, who is the heir apparent to the British throne, there will be a new line of succession.