A/N: There's a sweet, four line piece of meta on tumblr ( post/126707862562/doodlebrew-blaine-wasnt-really-sure-when-it) about the day Blaine realizes that Burt calls him 'son' instead of 'Anderson'. This inspired me to think what would happen if canon Kurt got together with canon Sebastian? How would Burt react? Needless to say, I couldn't fit it all into four lines. I hope you like it :)
(The title is in reference to the idea that Finn would have been Burt's "other son", so Sebastian would be his third son.)
Sebastian didn't think there would ever come a day when Kurt's father didn't look at him like he was a complete and total bastard.
And why shouldn't he? That's exactly what Sebastian was – that's what he had been to Kurt for a good portion of Kurt's senior year. From the day they met and shook hands, all he had ever done was scheme to ruin Kurt's life, and for what?
Kurt thought it was for Blaine, but that wasn't true entirely.
It was because Sebastian liked to win. He liked to be the best. Kind of in the same way people get addicted to auctions on eBay, in the end overbidding outrageous amounts for worthless junk just so that someone else doesn't beat them to the punch.
From the first day Sebastian walked through the doors at Dalton, all The Warblers ever talked about was Blaine, Blaine, Blaine, Blaine.
That meant Blaine was the best.
That meant Sebastian needed to have Blaine.
But that was because The Warblers hadn't spent enough time with Kurt to know that he was the one – the real deal, true holder of the title 'sex-on-a-stick-and-sings-like-a-dream'.
Unfortunately, Sebastian didn't figure it out himself until the damage was done.
Until he'd almost blinded Blaine.
Until he'd blackmailed Rachel.
Until David Karofksy tried to kill himself.
Sebastian made amends. He had apologized; he even meant it. Hell, he helped Blaine propose to Kurt the following year.
In a strange twist, when that engagement fell through, Kurt thought Sebastian would make a play for Blaine, but he went after Kurt instead.
And he won him.
Kurt managed to forgive Sebastian. It took a while, but it finally did happen.
Once Kurt's friends saw how happy Sebastian made him, they warmed up to him, too.
But Burt never seemed to.
Burt was polite, but quiet. When Kurt invited Sebastian over for dinner, Burt held his tongue. When Kurt moved into Sebastian's penthouse, Burt told Kurt to be careful.
On the day Sebastian asked Burt for Kurt's hand in marriage, Carole clapped her hands and cried with joy for her stepson.
Burt simply asked Sebastian if he loved his son.
"Yes, sir," Sebastian said. "Yes, I do."
Burt nodded.
"Well," he said, "if Kurt wants to marry you, I'm not going to stand in his way."
And that was that.
Many of Kurt and Sebastian's friends made speeches at their wedding. Most of them talked about how Sebastian had changed for love, how he had changed for Kurt.
Burt made a speech, too, but it focused on his son – about how proud he was of Kurt, how strong Kurt was, how much he'd grown. He called Kurt a kind and compassionate young man who took after his mother. He said that Kurt loved completely and with his whole heart.
He said Sebastian was lucky to have him.
To Kurt, it touched him to hear his father talk about him that way.
To Sebastian, it sounded like a warning, one that was very clear.
Kurt is the best thing that will ever happen to you. Take care of him, with an or else firmly implied.
Sebastian did take care of Kurt, supported him, gave him the kind of life that allowed him the freedom to pursue his passions, and bit by bit, from birthdays and anniversaries to Thanksgivings and Christmases, Sebastian began to win him over. It came in the form of invitations to see the Buckeyes play, fishing trips on the Auglaize River, secret excursions to Kewpee's for a bacon cheeseburger while Kurt and Carole hit the Black Friday sales.
But it was on the day Kurt and Sebastian's son was born that Sebastian noticed it.
He was standing in a hospital birthing room beside his husband. The lovely woman they had chosen as their surrogate placed his newborn baby in his arms, and Sebastian, overwhelmed, began to cry.
Burt came up to him, put a hand on his shoulder, and, biting back his own tears, said, "I'm proud of you, son."
And that's when Sebastian knew he had truly won.
