Office of U.S. Sen. Rob Portman/AP Photo

Two weeks after his Republican senator dad announced his support for gay marriage and one day before the Supreme Court is to hear arguments on the issue, 21 year-old Will Portman penned an editorial in the Yale Daily News describing how he came out as gay.

"In February of freshman year, I decided to write a letter to my parents. I'd tried to come out to them in person over winter break but hadn't been able to. So I found a cubicle in Bass Library one day and went to work. Once I had something I was satisfied with, I overnighted it to my parents and awaited a response," Portman writes.

"They called as soon as they got the letter. They were surprised to learn I was gay, and full of questions, but absolutely rock-solid supportive. That was the beginning of the end of feeling ashamed about who I was."

Read More at the ABC News Gay Marriage Topics Page.

In his piece Will Portman discusses the difficulty of coming out about his sexuality as his father was being vetted for the vice presidency. Though he admits that his coming out prompted he and his father to begin talking about the policy issues surrounding marriage for same-sex couples, Portman writes that he did not want his sexual orientation to become an issue during the presidential campaign.

"My dad told the Romney campaign that I was gay, that he and my mom were supportive and proud of their son, and that we'd be open about it on the campaign trail."

Portman continues, "When he ultimately wasn't chosen for the ticket, I was pretty relieved to have avoided the spotlight of a presidential campaign. Some people have criticized my dad for waiting for two years after I came out to him before he endorsed marriage for gay couples. Part of the reason for that is that it took time for him to think through the issue more deeply after the impetus of my coming out. But another factor was my reluctance to make my personal life public."

That "rock-solid support" that Will attributes to his father was made evident earlier this month when Sen. Portman publically reversed his opposition to gay marriage.

"I have come to believe that if two people are prepared to make a lifetime commitment to love and care for each other in good times and in bad, the government shouldn't deny them the opportunity to get married," Portman wrote in an op-ed that ran in the Columbus Dispatch.

Portman came out in support of gay marriage at a crucial time. This week the Supreme Court will hear arguments on Proposition 8 and DOMA, two potentially transformative cases regarding the very issue that Portman's son had been urging the senator to consider since he came out during his freshman year of college.