Don't use this as your main source of information on Norse mythology. Some things are only based on speculation and theories, not hard proof from any texts.
Also, Jotuns are gods of chaos (Not necessarily "destroy everything" chaos, but rather "not categorized and put in order" chaos) so their gender and sex is a bit muddy. The first Jotun Ymer had both male and female genitalia and mated with himself, and that set the tone for all Jotuns to come.
We don't know for sure who Heimdall's mothers are. We're told he has nine, so people just assume it's Ægir's nine daughters. We don't know for sure if Ran is mother to the daughters either, because only Ægir is mention as their parent.
A god named Lothur helped make the first humans, but because he doesn't appear anywhere else, people speculate Lothur is another name for Loki. Høner is said to be Loki's good friend, which strengthens the Odin, Høner, Loki connection.
In one text Odin is the father of Tyr, but in another Hymer is his father. Depending on what people prefer they might claim either Frigg or Hrodr is his mother, but neither is mentioned as his parents, just wives. That's why I just put both Odin and Hymer as Tyr's parents. Male Jotuns could give birth, so there's nothing standing in the way of this.
People speculate that Skadi may originally have been a male deity because a man with the same name who is also associated with winter, snow and hunting appears in one of the Eddas. This could mean she's the original father of Ull whom she shares a lot of traits with.
When Skadi and Njord's marriage doesn't work out, she runs off with someone else, but people can't agree on who. Most people say Od, though.