He was 36 years old when he began a sexual relationship with 13 year old Lidia Pereprygina. He impregnated her and the baby died. When she fell pregnant again, he ran away and left her to raise the child alone. Lidia was not the only victim. According to various testimonies from the book Young Stalin by Simon Sebag Montefiore, Stalin had a pattern of pursuing underage girls. Lidia Pereprygina had barely entered puberty when Stalin raped her. Its quite understandable why so many have labeled Joseph Stalin a pedophile. Even in the crumbling Russian Empire, the age of consent was 14. Meaning both legally and morally, Lidia Pereprygina could not consent. Stalin committed statuatory rape.
Something to keep in mind, Stalin was from Georgia. So in that culture and at that time, it was bad, but not so bad as it might be seen today. It was extremely common for girls to be married off when they were 16, in some cases 15. But the issue back then, the consent was not just coming from the girl herself, but from her father (and by implication the mother too). That would have been seen as reprehensible, but not for exactly the same reasons as today. What would have been reprehensible is not staying with her, trying to seek her hand in marriage from the father. That was the type of thing many men would have been beat up over, sometimes to the point of death, even if they were the same age as the girl. Georgia was a Christian country and the situation would have been even more extreme in the Muslim countries to the south at the time. Remember, people didn't just have casual sex back then. Sex was connected to marriage. This was a time in Europe, however, where morality was just beginning to rapidly change. Many of the atheists and early communists eschewed the former "taboos". Georgia was still overall more traditional than Russia at the time.
Although this happened while Stalin had been exiled to the relatively remote region of Siberia. story here that found genetic proof that Stalin did father a child with Lidia Pereprygina: http://siberiantimes.com/other/othe...is-grandson-of-josef-stalin-dna-test-reveals/
Age of consent has always changed according to societal needs. Its been as low as puberty when we needed population. There is no official thing that is right or wrong except what society says.