The JDU's Iftaar party, which was organised at Haj Bhavan in Patna, coincided with the party at Tejashwi Yadav's house. When asked about the JDU party, Mr Sinha said he didn't know about the Iftaar at Haj Bhavan.
After attending the RJD Iftaar, Mr Sinha said: "It is an auspicious and happy occasion. Iftaar parties are a part of our composite culture. Lalu Prasad (RJD chief) is my dear friend. I am delighted to be among my family friends."
Asked whether his presence at a function hosted by an opposition party leader while skipping the one hosted by an ally of his party could lead to bitterness, he said "Iftaar only sweetens relationships".
The actor-turned-politician spent close to half an hour at Mr Yadav's residence, where Lalu Prasad - sentenced for fodder scam cases and currently out on bail for medical treatment - was not present.
Tejashwi's elder brother Tej Pratap Yadav, lawmaker, and eldest sister Misa Bharti were also present at the Iftaar, seeking to put to rest recent speculations about sibling rivalry that was triggered by a tweet from Tej Pratap.
Shatrughan Sinha has an acrimonious relationship with the BJP leadership. He has been making sharp comments against the BJP leaders, including Prime Minister Narendra Modi. He had recently attacked the BJP for trying to form a government in Karnataka.
"Sir, why are (sic) we playing with fire? Votaries of democracy are making a mockery of the system. Those who do not forget to sermonize on the value of democracy are out to wreck the polity. This politics of jugaad and arm-twisting or for that matter Dhanshakti over Janshakti is neither acceptable nor desirable. Sir, there is a saying you cannot fool all the people all the time to win/gain anyhow by hook or crook and a moreover the same is not advisable too," Mr Sinha tweeted.
The Congress and JDS later stitched a post-poll alliance to form a government in Karnataka.
With input from agencies