A Course in Miracles clearly says (repeatedly, the whole text through lol) that special relationships of any kind are an ego illusion and identification - in fact the ultimate one, because they are tied to your identity and the other person's identity.
Also by singling out one part of the Sonship, you tend to exclude the rest of the Sonship.
So, all relationships should be equally important all the time.
You achieve this by taking time (past and future) out of the equation - when you see anyone, you see them only now.
It is only the past that you share with the person that makes the special relationship relevant - and the future you PLAN to share with them.
Once reduced to the now and ONLY what and who you see in front of you, all relationships are equal.
However the Holy Spirit understands that you can't just give up your special relationships immediately in this world, and so offers a solution - dedicating them to holiness so that they may be used to return you both to the Sonship.
Prayer to dedicate relationships to holiness
I desire a holy relationship for myself so that I may share it with my brother whom I love.
It is not possible for me to have a Holy Instant without my brother, or for him to have one without me - yet it is wholly possible for us to share one now.
And so I choose this instant as the one to offer the Holy Spirit, that His blessing may descend on us both, and keep us in peace.
Holy Spirit, take this relationship and dedicate it to Holiness so that my brother and I may walk in the love of God, complete once again.