Illinois State Rep. Ed Sullivan Jr. on Sunday became the second Republican to endorse a gay marriage bill.

The bill, which seeks to make Illinois the 10th state to legalize such unions, awaits a vote in the House after passage in the Senate.

Sullivan, who previously opposed civil unions, told the Chicago Tribune that his mother-in-law is gay.

“The first reaction from people might be, 'Well he might be voting for that just because of his mother-in-law,'” Sullivan said. “The reality is, because my mother-in-law is gay, I have more of an understanding and familiarity with same-sex couples.”

“There is tremendous momentum leading up to this vote. I think we're very close. There's many of my colleagues that have talked about this, that have said it's the right thing to do.”

“I personally believe it is in line with what our party believes, and that's trying to treat people with fairness,” he added.

Republican Rep. Ron Sandack also supports the measure.

House lawmakers return to work on Monday after a two-week break.