( LifeWire ) -- First comes love , then comes marriage -- or at least that 's how the saying used to go . An increasing number of heterosexual couples have been shacking up without plans for a trip down the aisle . Angelina Jolie and Brad Pitt are raising four children together . Pitt has said the couple wo n't consider marriage until same-sex couples have the right to wed . According to a 2003 U.S. Census Bureau report on families and living arrangements , 4.6 million U.S. households were occupied by unmarried couples of the opposite sex . That 's up from 2.9 million in 1996 . `` People do n't question , 'Why did you get married ? ' They only ask you , 'Why have n't you gotten married ? ' `` points out Marion Willetts , an associate professor of sociology at Illinois State University . `` I think a lot of people feel if you were really serious about your partner and your relationship , then you 'd get married . '' But from what Willetts has found with the life partners she 's spoken to , that is simply not true . `` They 're in this for the long haul , '' she says . `` This is n't just some convenient thing or trial marriage . They 're just as committed to their relationship as married people . '' While Census data does n't identify couples who have sworn off marriage , Willetts has followed this group in a study of 83 couples she 's surveyed over the past few years for her current research , tentatively titled `` Union Quality Comparisons between Heterosexual Licensed Domestic Partners and the Legally Married . '' According to her research , it 's not just 20-something social idealists who decline to get married . Willetts has interviewed octogenarians in committed relationships who are not planning to tie the knot . In fact , according to a 2003 AARP survey of 3,500 single Americans aged 40-69 , just eight percent cited finding someone to marry as their reason for dating , while 49 percent said they were looking for someone to talk with or do things with -- in other words , a companion . As the prevalence of unmarried couples rises , more companies and state and local governments are providing a range of domestic partner benefits . Some , like New York state , require that medical benefits be extended to both same-sex and opposite-sex domestic partners , according to the Human Rights Campaign Foundation . Other states , like Illinois extend such benefits only to same-sex partners . Why do some couples opt for long-term companionship instead of legal marriage , like movie actors Goldie Hawn and Kurt Russell , who have been together since 1982 ? Alison Hatch , 30 , a part-time instructor and doctoral candidate in sociology at the University of Colorado at Boulder , and Daniel Welch , 31 , an elementary school teacher , cite reasons both social and political . `` We are philosophically opposed to marriage for a few reasons , but mostly because we do not feel as though we can in good conscience enter into an institution that actively discriminates against gay and lesbian couples , '' says Hatch , who has lived with Welch for four years . `` It is our belief that it is inherently discriminatory to grant social benefits to some couples and exclude others . '' Actor Brad Pitt told Esquire magazine in October 2006 that he and actress Angelina Jolie -- with whom he is raising four children -- have declined to consider marriage until same-sex couples have the right to wed. Partners choose not to marry for other reasons . Hatch , whose dissertation examined 48 committed heterosexual couples choosing to not pursue legal marriage , has spoken to people who feel marriage is a patriarchal institution . Some are against the intertwining of church and state in marriage . There also are emotional reasons why committed couples choose to stay unwed . `` I think that a lot of people like the kind of organic nature that your relationship takes on when you decide not to marry , '' says Julie Bluhm , 31 , a Minneapolis , Minnesota-based clinical social worker and a board member of the Alternatives to Marriage Project , a national nonprofit organization advocating equality for unmarried people . `` It 's almost a deeper appreciation of their relationship and the privacy of it . '' Being unmarried was not necessarily an obstacle to parenting for a small group of couples in Willetts ' research . In a study published in the Journal of Marriage and Family in November 2003 , two of 23 couples Willetts surveyed had children biologically related to both partners , though several couples had children biologically related to one partner -- typically the result of a previous marriage . Of the two couples , one pair had been living together for over 15 years and did not encounter any legal issues concerning their children by not being married . Said Willetts , `` They expressed to me that everyone -- including their children 's friends -- had just assumed they were legally married anyway . '' E-mail to a friend . LifeWire provides original and syndicated lifestyle content to Web publishers . Jocelyn Voo is a freelance journalist and relationships editor at the New York Post .
It 's not just 20-something social idealists who want to get married . AARP research shows many older couples marry primarily for companionship . Some couples see discrimination against gay and lesbian couples as reason .