When I perceive that someone has done something to me, it is really my subconscious trying to illustrate some issue within me that is not healed.
Why do I project that particular error onto my brother or sister?
To understand and heal this, I must go deep to find the source of that projection - why that exact error? Sometimes it is like peeling an onion, there are many layers all of which can cause tears...but keep going to the origination of the so-called sin.
Once you find THAT and have healed it, forgiven it, you never have to do that error again.
(If the same sin reoccurs, then you know that you did not find the source of the sin and there is more work to do.)