Before filming for the Netflix series, Jason had dated Mary for four years.
They adopted dogs together and still share custody of their beloved pets.
Speaking out on his friendship with ex-girlfriend Mary, Jason said: “Mary and I understand that our situation is unique and that many find it hard to be close friends with an ex.
“The way I see it, you choose to be with someone because you love and value that person as a friend.
“So just because you break up and are no longer romantically involved shouldn’t mean that you aren’t able to still respect and love that person as a friend.
“My ex-girlfriend before Mary is also one of my closest friends, as is her husband.
“If you treat your significant other with respect and you don’t do anything to violate his/her trust, then I see no reason why, with time, you can’t be friends after a breakup.”
Selling Sunset is available to watch on Netflix.