A Sydney-based gay couple aged in their late eighties, who have been in a relationship for 48 years, say they want the right to marry before they die.

After a lifetime of relative privilege and opportunity, it is the one thing that eludes John Challis, and at 87, it really bothers him.

"I'm not going to live forever," he said.

His partner, Arthur Cheeseman, who is 83 and has trouble seeing and hearing, was not well enough to take part in an interview.

"He is getting frail", Mr Challis said.

"We met at the Art Gallery of New South Wales; it was the final night of the great Sydney Northern retrospective in 1967.

"We just happened to walk out the door of the gallery together and smile at each other, and went off and had a cup of coffee and then there you are."

Now the lengthening shadows of their lives give urgency to their wish to finally have their relationship given the public status it deserves.

"We had a lot of common interests in music, in gardening, in architecture," Mr Challis said.

"We were just sort of very compatible and just grew together year after year after year, and here we are looking after each other in our old age."

Mr Challis worked for many years at the ABC, while Mr Cheeseman worked as a pharmacist.

"Arthur and I have lived together for 48 years. We've been a very normal suburban kind of couple," Mr Challis said.

More recently, the couple have given up their time to speak on behalf of Australia's elderly gay community in the marriage equality debate.

Mr Challis believes the law reform cannot pass until Prime Minister Tony Abbott first abandons his faith-based opposition to marriage equality for same-sex couples.

"I'm sure our relationship is just as devoted as his is and why [should] we be looked at in any different way?"

When Coalition MP Warren Entsch presented his bill to legalise same-sex marriage into Federal Parliament, he offered John Challis and Arthur Cheeseman as examples of ordinary, same-sex Australians who want the law to change.

The bill was co-sponsored by six MPs from across the political divide.

Mr Entsch said it was about promoting an inclusive nation, not a divided one.

"A divided nation is what we will be if we continue to allow discrimination", Mr Entsch said.

Mr Challis agrees.

"What we feel is that recognising gay marriage would simply crown the whole process of gay rights and give gay people exactly the same status and dignity in society as heterosexual people," he said.

For now, he can only dream about what that day would be like.

"We will simply go down the registry office very quietly with a couple of very close friends.

"It's just a legal function as far as I'm concerned to get that legal status, so that our relationship has exactly the same status, exactly the same dignity, exactly the same standing as Tony Abbott's relationship with his wife.

"I mean I'm not interested in any sort of great marriage celebration and all the rest.

"We might just have a few drinks with our friends or something like that - if it ever happens.

"But the way things are going, I doubt if it will happen in my lifetime."