If you are not forgivable, neither is your brother.
You can't have it be that you are reluctant to forgive your brother, believing that you're able to forgive yourself but not him. If you don't forgive him, you do not forgive yourself.
The ego's view is always that something different applies to others than applies to yourself. Always there's a different set of rules and judgements that it allocates to your brother, in the claim that because the rules for him are different to the rules for you, there is a separation between you.
In that sense, the ego uses separation as a kind of barrier of protection. It uses separation to try to treat your brother in a certain way, which is different from how you treat yourself, and to then protect yourself from the effects of that different way of treating him by being separate from him.
Always the ego is believing that what applies to you does not apply to him, and what applies to him does not apply to you.
But the metaphysical law of God is that the same laws and truths apply equally to everyone everywhere all the time.
To be in the Holy Spirit's thought system you MUST accept that what applies to you and your brother MUST be the same. If its true of him, it is true of you. If its true of you, its true of him.
Therefore, you MUST be willing to forgive your brother IF you are to forgive yourself. IF you are holding a grievance, then even though it seems like it is a grievance about someone separate from you, as though it does not apply to you, IT IS about you as well.
There is no escaping this law. What you do unto others you directly do unto yourself. Any appearance that this is not the case IS an illusion, and believing it is extreme denial and egotism.
This also means that if you are working on forgiving yourself, you ARE working on forgiving your brother simultaneously. And vice versa. It also means if you are taking your forgiveness all the way to the atonement and supposedly claiming it for "yourself", you ARE claiming it also for your brother.
The forgiveness that applies to you applies to him equally. As you heal, you become the healer. As you accept you are forgiven because you did not really sin, you accept that others are forgiven because they did not really sin. As you become willing to receive God's love because you are worthy of it, you become willing to allow others to receive God's love through you because they too are worthy of it.
The separation doesn't just keep you separated from your brother, it keeps your brother separated from you. It's a two-sided separation. If you lift away the separation that is dividing you from your brother, you aren't just lifting away separation from yourself, you're lifting it away from both of you, making you joined as ONE.
This lends new meaning to "what is mine is yours". Oneness.