Being in a long term relationship is serious business, and those who want it to last should make sure they are being faithful to their partner. It often seems to people that cheating on a partner is the only way a person can be accused of relationship betrayal, but it takes many different forms. Words and deeds are both important when it comes to being committed to building a life with another person, and any type of deviation from supporting a partner in front of others can be considered betrayal.
Families are often the source of difficulties between couples, and asking a family member to agree with them on an issue instead of a spouse is encouraging breaking the bond between the pair. Friends can also do this, but it occurs less often. These are the types of betrayals that happen all the time, but only some of them can be healed well enough to keep the relationship from failing.