I must admit I thought it was strange, then my wife toldme about so called "victorian marriages". I did some research, and it was quite common in those days, even today. For people to sacrifice fleshly desires, to give themselves to the Lord. The apostlePaul stated that it be better for a Christians to be single, than to get married, why? because it hinders service to theLord, because the spousebecomes the first object and then the children.
However, there were those who decided to get "married" for the sake of having companionship in their service to the Lord. Some decide to not marry at all and to remain chaste. Someone once mentioned that Russell remained a virgin because the 144,000 were said to be virgins, "defiled not with women" but this doesn't jive with his comments on that verse.
Apparently, Maria Russell, who by the way was older from my calculations...entered the marriage with sacrificing their sex life. Although Russell admits to affectionately kisssing his wife several times a day.
It's possible that with Maria's sister getting married and having children, that maria began to feel maternal and wanted to break those vows of chastity, and Russell was not willing, and it caused a strain in the relationship.
Today there are sexless marriages, some by choice, others by fate.
RR