The trial that will decide if Michigan's same-sex ban is constitutional begins Tuesday in Detroit.
One of the key issues is expected to be whether children raised by same-sex couples are worse-off than kids raised by heterosexual parents.
It's a case that started in 2012 with a lesbian couple near Detroit who sued after learning they could not jointly adopt their children because of the ban on gay marriage approved by voters in 2004.
"As a parent you should worry about your kids, should worry about how they're doing in school, their health, you shouldn't have to worry about if they're going to be taken away from you if something happens to your partner," said Tom McMillen-Oakley who lives in Jackson with his husband and their two adoptive children.
Tom and his partner Tod married in 2008 in California and have two children, Anna, 9 and Eli, 5, but only share legal custody of their daughter.
"By the time we got married and Eli came along the judge was no longer doing second-parent adoptions, so I am Eli's only legal guardian, Tom has no ties to him at all," Tod said.
The couple compared their situation to that of April DeBoer and Jayne Rowse, the two Detroit-area nurses who are challenging the ban.
The McMillen-Oakley's are hoping a favorable outcome can bring security to their family.
"It's the stuff that causes me to lay awake at night and wonder what if something happened," Tom said. "The 'what if' questions are the ones that always get to you."
In the trial that begins Tuesday, questions over same-sex parenting and the welfare of children of same-sex couples are expected to be front and center. Scientific studies on same-sex parenting will be put through the legal wringer and both sides claim to have science on their side.
"This trial will be the first time this research is put on trial and so you will have experts on both sides," said Michael Sant'Ambrogio, a professor of law at Michigan State.
"The consensus among sociologists is that same-sex marriage does not harm children, so this new research it's an outlier in terms of the field but it will be put on trial."
Sant'Ambrogio also drew comparisons to a similar case in California in 2010 which not only challenged same-sex marriage but examined the welfare of the children of same-sex couples.
In that case a federal court ultimately found the same sex-marriage did not harm the children.
Meanwhile, dozens of pastors from around Michigan gathered Monday in support of the state's ban.
"Marriage is a covenant between a man and woman," said Randy Heckman with the Michigan Family Forum.
"We need to understand from our knowledge of how things work to attempt to run counter to God's established order ultimately hurts even those who seek to redefine marriage."