Lithgow married teacher Phoebe Jean Taynton (six years his senior) at the age of nineteen back on 10th September 1966. This was just before he graduated from college.
They have one son together, Ian, who is also an actor and appeared in 3rd Rock From The Sun alongside his father.
Lithgow and Taynton separated after he reportedly had affair with Liv Ullman and seven others while with married to her. (www.telegraph.co.uk)
In an interview with usatoday.com he recalled "I was a deeply confused young man."
Their divorce was finalised in 1980. Not long after his friend set him up with Mary Yeager whom he has been married to since 12th December 1981.
On their first date he remembered; "she was all turned out, and I was in sweaty tennis gear." Within just a couple of weeks they were talking about getting married. In December 1981 they wed; "Mary is a wonderful combination of earthy and intellectual. We both feel like country bumpkins in Los Angeles. I'm an Ohio boy, and she's a Montana girl. Yet we're both very educated." (www.pepople.com)
The pair now have two children together; Phoebe and Nathan.