Step One: Assume all of them are right
Malicious feedback or reviews are rare. Assume that people actually mean what they say. Look at it without discarding it immediately. Put your feelings aside for the good of the game.
Step Two: Understand that everyone is subjective
People give you their opinions based on their expectations, experience, personality, mood of the day, etc.
"The game is too difficult" and "the game is too easy" is not conflicting feedback. It is two different pieces of feedback from two different people. One of them found it too hard, the other one too easy.
Step Three: Understand what exactly they mean
Friends and family have the advantage that you can ask for clarification. Otherwise you need to read between the lines and guess. But "too easy" is not enough. What is it that was too easy? Your (in my example) seemingly conflicting feedback may not actually be conflicting at all. Maybe these two people speak about different aspects altogether. Maybe the "too hard" player died three times and decided that means the game is hard, while the "too easy" player understood that dying and respawn is simply part of the game.
Case in point: My recent strategy game is considered "too hard" by some people. Heck, one of them wrote "This is the Dark Souls of strategy games". That's because losing units and buildings is pretty much normal and will happen, no matter how good you play, but some people play with the assumption that losing a single unit is the start of a downward spiral.
Step Four: Address the issues
Now you understand (or at least have a guess) where the players are coming from, what they expected and what in their eyes is a problem. With that knowledge, you can address the issue. Maybe the game really is too hard. Maybe the difficulty is right but it appears to hard (see my example) and you need to communicate more clearly what players should see as setbacks and what not.
For example: In an FPS shooter or RPG, if you die, lose all your gear and respawn at the start of the level with all enemies respawned, the game communicates that death should be avoided. If you die and lose nothing, respawn near where you died and dead enemies stay dead the game communicates that death is just a small setback. In the first case, players are tempted to reload a save, in the second case players are incentivised to just keep playing.
Especially what you consider conflicting feedback rarely means what the players say it means. Often the issue is somewhere else entirely, often in player expectations. DOOM had an easy difficulty setting named "I'm too young to die" with an icon of the player with a baby hat - clearly communicating that it exists, but it's not how the game is meant to be played. Divinity, Wasteland and other RPGs communicate their difficulty settings by giving a player the choice to focus on the story (with easy combat) or on tactical combat.