A few salient facts are known about the Americans whose lives might be changed by a Supreme Court ruling on same-sex marriage expected this summer. About one in five gay and lesbian couples are raising children that are under age 18. Same-sex couples are less likely than traditional married couples to have health insurance covering them both. One in 10 men with a male partner or spouse is a military veteran. As many as 6 million Americans, roughly 2 percent of the population, have a parent who is lesbian, gay, bisexual or transgender.