I don't think it would be accurate to say the Jesus was a member of the Mormon church. It would be more accurate to say that his children are members of his church, and that the Church of Jesus Christ of Latter Day Saints is the present day manifestation, or organized visible community, authoritatively representing his gospel and plan of salvation. This church has had different names and even very different practices and doctrinal imperatives (the Law of Moses) in different times and places, but all are instances or manifestations of the same gospel, which, in LDS theology, are known more or less, in different dispensations among disparate peoples.
Some comments and questions:
1. Jesus was a Jew, not a Christian, not a Mormon. Yet you say Jesus' church is the same as the ancient church (different practice, different laws, but the same church). So are you saying the Jews are Christian?
2. We are not Jesus' children. We are Father's children, the same as Jesus is a Son of God, and thus one of his children. It would not be more accurate to say anything about "his [Jesus] children", except the children in his direct line (of which we have no record; we don't even have a record of Jesus being married).
3. What exactly do you think the gospel contains? What, if anything, has changed?
4. If the laws and practices change with each dispensation to be culturally competent, how can it be accurate to say it's the same church?
5. Why does the modern church not look at all like the records we have of the ancient church? That which Joseph restored bears little if any resemblance to what Jesus created.
6. If Jesus' church was Moses' church, and the two are diametrically opposite, why do you think they are manifestations of the same concept?