A mentor is not a surrogate parent. Although this should be obvious I have met mentors who somehow, along the way begin to behave as if they are the parent, although they are one with no authority. When the mentor arrives at this conclusion they have left their moorings as a mentor and are embarking on a new journey. Don’t mix the two.
There are several reasons why this line should not be crossed. The most important of which is that a child no matter how badly he has had it, will always love and desire to have his own parent’s, not a surrogate. The greatest strength of a mentor is that no matter what happens the mentor continues to be involved in the life of his mentee.