A man who is married with children but starts another family with another woman (intentionally) and wants to carry on a relationship with both women as if it is a normal way to live. He has half of his belongings in each woman's house. Sort of like polygamy but with only one marriage involved and one fiance. He likes to spend holidays with both families at the same time. This man is more of a sociopath than a polygamist.
Man that spends his life legally separated from his wife (never intending on getting divorced) while dating and getting engaged to various other deluded women. He cohabitates with both women at the same time.
*This works very easily for a Canadian working in the United States.
Mark was married but fell in love with a co-worker so he became a 2fam man because he wasn't interested in divorcing the wife his fiance didn't know he had.