I have understood that the covenant about a kingdom is a separate covenant from the new covenant. But I know that the JWs do not separate them.
But I have seen in the Bible that the new covenant is about forgivness of sins through Jesus' blood. And I have not seen in the Bible that the new covenant is about the kingdom.
Jeremiah 31:31 “Look! The days are coming,” declares Jehovah, “when I will make with the house of Israel and with the house of Judah a new covenant. 32 It will not be like the covenant that I made with their forefathers on the day I took hold of their hand to lead them out of the land of Egypt, ‘my covenant that they broke, although I was their true master,’ declares Jehovah.” 33 “For this is the covenant that I will make with the house of Israel after those days,” declares Jehovah. “I will put my law within them, and in their heart I will write it. And I will become their God, and they will become my people.”
34 “And they will no longer teach each one his neighbor and each one his brother, saying, ‘Know Jehovah!’ for they will all know me, from the least to the greatest of them,” declares Jehovah. “For I will forgive their error, and I will no longer remember their sin.”
Also explained in Hebrews chapter 8 and 9.