By a twist of fate, the illegitimate son of the Marquis's family marries the county princess.

[Female-oriented novel + male protagonist's perspective + 1v1]
The female lead is extremely possessive and spoiled; please do not read if you mind this.
After a stroke of good fortune, Wen Zongji transmigrated into the body of a concubine's son in a marquis's mansion, and his story begins with his wedding night with a county princess.
The original owner's ability to marry the eldest princess's legitimate daughter, Princess Anhe, as a son of a concubine in a marquis's household was entirely due to a twist of fate and a stroke of great luck.
Looking at his spoiled and willful wife who would throw tantrums and break things at the slightest disagreement, Wen Zongji felt utterly speechless.
But what's done is done, so let's just make the best of it!
In this era of clear social hierarchy among scholars, farmers, artisans, and merchants, Wen Zongji had only one path: the imperial examination. He did everything in his power to climb the ranks.