The 28-year-old wicketkeeper-batsman found his lady love, Pallikal, 22, after both ended up training under the same fitness coach here.
After a one-year courtship, both decided to get engaged at the ITC Chola last week.
Though Karthik could not find a berth for himself in the South Africa bound squad, yet, the Tamil Nadu batsman celebrated the occasion with a crafty 133 against Saurashtra in a Ranji Trophy match here today.
The couple also posted a photograph on Twitter soon after their engagement.
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After his divorce from his first wife Nikita, whom he married in 2007, Karthik had decided to focus only on cricket.
Both of them enjoyed each other's company in the course of their fitness sessions and somehow managed to succeed in keeping their affair away from the media glare.
Karthik featured in the ICC Champions Trophy as well as India's tour of Zimbabwe this year.
Pallikal is the first Indian squash woman to break into the top 10 in the world rankings and is one of the most beautiful sportspersons in the country.