Relationships are about (desire or want) and not "need".
There are only 5 "needs" we have as adults. Air, Water, Food, Shelter, and Clothing. Everything else falls under the category of (wants) and (would be nice to have).
When we love someone it means we enjoy their company and (want) to be with them. However if our mate died or the relationship ended it would not be the end of our existence.
It's romantic to say or be told, "I can't live without you." However the reality is we (can) live without them.