How do you prove loyalty?

Never cheat! If they are having personal problems or problems at work be there for your partner and remember that two heads are better than one. Remember special occasions such as birthdays, anniversaries, etc. LISTEN to what they have to say and expect the same back. Respect them and when they want 'head space' let them have it. We all need time alone. You are going to have to trust them and hopefully they meet up to your expectations. If they don't then you know at least you kept your end of the bargain. It's just not about loyalty, but EVERY feeling you have for your partner (the good feelings) should come from the heart.