Assalamu Alaikum wa rahmatullahi wa barakatuhu.
My question is that the Christians use this term "God's Kingdom", referring to the heaven. The Christians believe that Jesus (Isa) Alaihi salam will be the co-ruler. Do we Muslims believe in this term. I am sorry if I didn't make you understand. May Allah forgive me. Jazak Allah Khair for answering my question.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The term ‘God’s Kingdom’ should not be used to refer to Paradise because there is no evidence about this in the Book of Allaah or the Sunnah of the Prophet, sallallaahu the Sunnah 'alayhi wa sallam. In addition to this, it might be understood that it is only Paradise that is the kingdom of Allaah, whereas the entire universe is part of His Kingdom. Allaah Says (what means): {Say,” O Allaah, Owner of Sovereignty, You give sovereignty to whom You will and You take sovereignty away from whom You will.} [Quran 3:26]

Our belief in ‘Eesa (Jesus) is what is mentioned in the Quran and in the Sunnah, that he is a slave of Allaah and His Messenger, and we do not believe that he is a Lord or a God or that he is a partner with Allaah in anything in His Sovereign, because all this is clear disbelief (in Allaah).

For more benefit, please refer to Fataawa 88187, 87745, 85366 and 84206.

Allaah Knows best.