Piotr Yevstigneyevich Rasputin's Links
Found him as a small kid on the streets. Adopted him as his son despite having a straining relationship with his own father. Piotr won't deny that there were times were he treated Mikhail bad as well, but ultimately tried his hardest to correct himself and ask for forgiveness.
The relationship he had with Immanuil was a bit more strained than with Mikhail. As Immanuil was only a soul residing inside Mikhail it was harder, especially that in the beginning it appeared as if Mikhail was either possessed or mentally ill. Nowadays they get long well, though Piotr is still caugh off guard about Immanuil's impulseness and hyperactivity.
Early on had a slightly strained relationship with him but as he grew older and was given more independence he had enough time to think about things and to forgive the past. Ultimately Piotr was the one who saved him after all.