Any children born while the Queen is still alive will be her great-grandchildren and therefore not entitled to the style of HRH, unless special letters patent are issued. This was done shortly before the birth of Prince Charles to allow him and Princess Anne to be HRH, which they would otherwise not have been at birth, being grandchildren of the monarch through the female line.
With regard to marrying commoners, the last 'non-commoner' to marry into the Royal Family was Princess Marina of Greece and Denmark in 1934, Duchess of Kent.
I once knew an electrician who went for a plug - it was shocking.......
As we are talking royal families, the old story goes a teacher asked her class to name the three things that the Kings brought to Jesus to improve his life. Little Johnny answered, "Drin-king, smo-king and bon-king"
someone on tv. just said its a very good thing they have known each other for such a long time as" she knows she is marrying a bald man ".......love it !
I did say 'non-commoner'. I meant Prince George, the previous Duke of Kent, the present Duke's father. I should have been more precise by stating woman, as Prince Philip has Greek royal blood, although he had to give up his title when he became a British citizen, which is why the Queen created him a prince of the UK in 1957.