As for marrying and records and such. In the early years of the church, records of memberships, marriages, and such were at time sketchy. Sometimes non-exsistent. The early time in The Church of Jesus Christ of Latter Day Saints (LDS)/aka Mormon was very volatile. Most people did not receive the Mormon Message well. There were many deaths. The members of the church even had to hide the murdered prophet, Joseph Smith's body - their prophet,so the mobs wouldn't take it. Members fled to different areas. I can see why there may not be records of marriages, births, deaths, etc.
Marriage registration was variable in each state. I have ancestors from OH and marriage records started in the 1830's. But in Michigan, as early as 1867. Of course, if you know which church the ancestor attended/religion, you might have better luck. That is assuming there were an catastrophes that damaged church records.
"It seems enough that the people concerned knew they has been through the ceremony conducted by the priest. I have seen plenty of death certificates bit not one marriage certificate. "~~This is an interesting observation.
I have many LDS friends. I will ask a few and get back to you. They might provide some insight and links to help with your research.
Male members of the church, worthy of such, would "earn" or "prepare" to receive the priesthood. (
https://www.mormon.org/faq/purpose-of-priesthood)
There are different levels of the priesthood. The younger boys were often deacons. They could bless and serve the sacrament. Adult men would work toward becoming an Elder. An Elder can perform rights in the temple (with training). They can marry people outside the temple in a civil ceremony. They can also perform blessings. For those who are sick or troubled.
So, an Elder in the church, including the male ancestors you are researching, I would believe held the priesthood. They can marry persons. Also, in order for them to get married/sealed in the temple, they would have to hold the priesthood/maintain a worthy office of Elder. Does this make sense?
Sorry if this seems jumbled. I worked a night shift and hope it makes sense.