WASHINGTON — The first formal step in the marriage cases before the Supreme Court happened Friday, as the same-sex couples in four midwest states asked the justices to strike down bans that prevent them from marrying or having their marriages granted elsewhere recognized in the states.

When the court announced in January that it would be hearing the cases out of Kentucky, Michigan, Ohio, and Tennessee, it set a schedule requiring the couples or, in one case, widower, to file their briefs with the court by Friday.

In two of the cases — Kentucky and Michigan — lawyers for same-sex couples argued that the Constitution requires states to license same-sex couples' marriages. In the Kentucky case, as well as in the Ohio and Tennessee cases — lawyers argued the states must recognize marriages of same-sex couples that were granted elsewhere.

The first brief whose filing was announced on Friday was in a pair of cases out of Ohio, both of which deal with recognition of marriages previously granted to same-sex couples in other states. The brief's filing was announced at 10 a.m.

Shortly thereafter, the couples in Tennessee — also seeking recognition of their marriages granted elsewhere — filed their brief, as did couples in Kentucky seeking the right to marry and the right to have marriages granted elsewhere recognized.

A bit before 11:30 a.m., the final brief came in from the Michigan couple seeking to marry in that state.

The states' briefs defending the bans will be due in a month, by March 27.