Dear Prudence: Recently, my partner's lifelong best friend and his wife were killed in a car accident, leaving us with custody of both of their children. They are two wonderful girls ages 4 and 2 and we love them dearly and are happy to have them. Both of them are comfortable with us since we spent a great deal of time together before their parents passed away, but we did not have any children of our own and we are taking a crash course in parenting.

At this moment, I have two main concerns. One of them is that we are not sure how to help them understand what has happened.

My partner and I are confirmed atheists, and although our friends were not seriously religious, they did have some spiritual beliefs, and we are not sure whether they would want us to teach their daughters that they've gone to heaven or follow our own instincts to say that even though mom and dad loved them more than anything, they're simply not coming back.

Another concern is that before this happened, my partner and I were trying to conceive a child of our own. We've decided it's best to hold off on this for a while because we believe it would be too much for the girls (and us at this moment) to handle after such a loss. How much time does it take for a child to adjust to such a thing? Should we give up on the idea at present?

Prudence says: What a crushing loss for these tiny girls to absorb. Amid this tragedy, they are lucky that you and your partner are there to provide them with love and security.

Making such guardianship arrangements is a responsibility of parenthood; let this be a spur to those who haven't done so. As your case illustrates, the best guardians might not be family members, but dear and trusted friends.

You now have a large task ahead in becoming an instant family and creating a good life for two confused and frightened little girls.

For advice on what you should tell them, and what you should do about expanding your family, I turned to David Schonfeld, director of the National Center for School Crisis and Bereavement at St. Christopher's Hospital for Children.

He said there are four painful but essential truths that have to be conveyed age-appropriately to children who have suffered such a loss: Death is irreversible; all life functions end completely at death; everything alive eventually dies; there are physical reasons someone dies. Schonfeld is co-author of a pamphlet that gives instruction on how to explain these difficult concepts.

While acknowledging people's belief in heaven, he says conveying that to children, especially very young ones, can cause tremendous confusion. It's difficult to grasp the idea that your parents no longer exist here, but are in some other realm out of reach.

Since you and your partner are atheists, and your late friends didn't have a strong religious tradition, I think you should follow your own instincts about keeping things simple and factual. The girls' parents knew of your lack of religious belief and still chose you. As the girls grow up, if they develop an interest in religion, you can decide the best way to respect and foster that.

You do not mention that you are under the immediate pressure of a biological clock, so I agree with Schonfeld when he says now is the time to focus on making yourselves a family and seeing the girls through a traumatic transition. After you feel settled into being a unit, for which there isn't a timetable, you and your partner can explore the question of whether you want to add another child and when.

Bear in mind that the loss your girls have suffered is something they will deal with for the long term. It won't always be the primary focus as it is now for everyone, but it will echo through the years. Schonfeld says that with the help of the strong, loving, committed family you will be, the loss the girls suffered will simply be a part of their understanding of themselves, and will not keep them from forging happy lives.

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