If you are close with your family it could be a good place to start (depending on the advice required!) and may improve your bond with them. Otherwise, anyone you trust to be honest and has the experience to discuss the common sense in a time you might be love-blind.
You can go to anybody you feel comfortable with, be that your bff, 7 Cups, your mom, dad, brother, auntie, etc. You can go to any of these people because relationships are not just limited to boyfriend/girlfriend, husband/wife. It can refer to friendships, which count. So in essence everyone has had a relationship and can share their own advice on it.