Chelsea Clinton gives birth to second child

US presidential hopeful Hillary Clinton has become a grandmother for the second time after her daughter gave birth to a boy named Aidan.

Chelsea Clinton, 36, and her hedge fund manager husband Marc Mezvinsky already have a 20-month-old daughter named Charlotte.

Both Charlotte and Aidan were born at Manhattan's Lenox Hill Hospital.

On Twitter, Chelsea Clinton said the couple are "overwhelmed with gratitude and love".

Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky.

— Chelsea Clinton (@ChelseaClinton) June 18, 2016

Aidan is the second baby to be born to the child of a presidential candidate this year.

In March, presumptive Republican nominee Donald Trump's daughter Ivanka gave birth to her third child, son Theodore James.