The following verse is speaking of only "one" throne:
"And there shall be no more curse: but the throne of God and of the Lamb shall be in it; and his servants shall serve him" (Rev.22:3).
Here is what John saw and heard while he was at that throne, the throne of God and of the Lamb:
"And he that sat upon the throne said, Behold, I make all things new. And he said unto me, Write: for these words are true and faithful. And he said unto me, It is done. I am Alpha and Omega, the beginning and the end. I will give unto him that is athirst of the fountain of the water of life freely. He that overcometh shall inherit all things; and I will be his God, and he shall be my son" (Rev.21:5-7).
Here we read the one on the throne saying, "I will be his God." This is God speaking and since there can only be ONE who is the beginning and the end and the Alpha and the Omega, then it cannot be denied that the one speaking is Jesus Christ:
"And, behold, I come quickly; and my reward is with me, to give every man according as his work shall be. I am Alpha and Omega, the beginning and the end, the first and the last" (Rev.22:12-13).
These are the words of the Lord Jesus because He is the one who says,
"I come quickly" (Rev.22:20).
There is only "One" on the Throne of God and the Lamb, and that proves that the Lord Jesus is God--the Alpha and Omega and the Beginning and the End.
Do you deny that?