Actress Sally Field has written a heartfelt letter about raising her gay son Sam, in support of legal efforts to prevent US states passing anti-gay laws.

The Oscar-winning actress, who has two straight sons and one gay son, wrote the letter in support of the Human Rights Campaign.

She wrote: “Sam is my youngest son, by 18 years, and he’s gay. To that, I say: So what? Growing up, Sam wanted desperately to just be like his older brothers – athletic, rambunctious and even a little bit macho.

“He wanted to beat Eli at tennis, trounce Peter at computer football and learn everything about every basketball player on the court. But Sam was different. And his journey to allow himself to be what nature intended him to be was not an easy one.

“When I saw him struggling, I wanted to jump in. But his older brothers held me back. They told me I couldn’t travel that road for Sam. It was his to travel, not mine. I had to wait for him to own himself in his own time. I could make it easier only by standing visibly to the side, clearly loving him, always being there and always letting him know.

“Finally, at 20, long after he beat his brothers at tennis and computer games and knew as much as anyone about basketball, Sam was able to stand up proudly and say, “I am a gay man.”

“One of the great privileges of my life to have been allowed to be a part of Sam’s journey.

“There are people out there – organizations and politicians, strangers who have never even met Sam – who would rather devote themselves to denying his happiness.

“Why would anyone want to prevent my son — or anyone’s son or daughter—from having basic legal safeguards like family medical leave, Social Security survivors benefits, or health insurance? It doesn’t make any sense, but it won’t change until people speak out. I’m proud to stand with HRC to add my voice. Will you join me?

“Whether you are LGBT yourself, a parent or grandparent of an LGBT child, or just a great person with strong convictions about what’s fair and right, I hope I’ve convinced you to stand with HRC for equality. You’ll be glad you did!”