Marlin grew up in Highland Park, Illinois. He received a BA in Sociology from Tulane University in 1990. Upon graduation he relocated to Kyoto, Japan where he worked and studied for two years. Leaving Japan, he and a friend took a three-year, 20,000-mile, around-the-world odyssey on mountain bikes. The trip took him through the Himalayas, across parts of the Gobi desert, Tibet, India, Pakistan, through the middle-east from Syria to Egypt, across Eastern Europe and North America. Along the way he met and lived with nomadic peoples, matriarchal tribes, cave-dwelling ascetics, Muslims, Christians, Jews, Hindus, Buddhists, Shintos, Taoists, Jains and practitioners of traditional religions and studied religious scriptures and practices. Upon returning to the United States he entered Harvard Divinity School where he received his Masters in Divinity in 1999.
He was ordained as a Unitarian Universalist minister in 1999 and went on to serve the historic First Church in Boston. In 2000, at the age of 31, Marlin was called to All Souls Unitarian Church in Tulsa as the Senior Minister. All Souls is the largest Unitarian Universalist church in the United States with almost 2,000 members. In 2008, All Souls in Tulsa welcomed into their church a predominately African American congregation of 300 Pentecostal Universalists formerly led by Bishop Carlton Pearson. Since that time All Souls has created new worship styles and opportunities to meet the needs of a church that is growing in racial and theological diversity.
In 2010, he received the Humanitarian of the Year Award from the Unitarian Universalist United Nations Office for his work to end the persecution of gay and lesbian people in Uganda, Africa.
Marlin is married to Anitra Lavanhar and they have a son Elias who was born in 2000 and a daughter Lyla born in 2008. Their daughter Sienna was born in 2003 and died in 2006.