Getting custody of Alan, the little boy I’d hoping to adopt, became a real option very suddenly. Alan’s mother was in crisis, and something was going to have to be done to ensure his well-being.

I originally put myself forward as a kinship carer in the hope that we could keep him out of the non-kinship foster system. His mother and father would rather have me care for him than a stranger or another family member. While I would have always preferred to adopt him outright, I agreed to foster Alan for up to two years while his biological mother, to whom I am related, got on her feet. Any longer than that, I told her, would need to lead to adoption since he deserved stability.

Apart from his parents, the most important family members to get on board were my then 6-year-old twin daughters. Marie agreed right away that Alan should join our family. She’s the one of my daughters who is prone to anxiety, but she said that her heart knew the right answer right away.

Julie, usually the more empathic of my girls, needed more time. She put together a list of her worries. It took two days to talk through them all. We even pulled the school counselor into the discussion. Julie finally agreed to the wisdom of Alan’s joining our family only when I encouraged her to think to the future. “Imagine,” I told her, “that it’s your eleventh birthday. How do you feel if Alan is your brother? How do you feel if he’s not?” She had been too caught up in the one-week absence that my meeting with his social worker in the UK would entail to think about the long term picture. She was only 6, after all.

In the ups and downs that followed, there were moments when it seemed that getting custody of Alan would be impossible and others when it felt like a done deal. The biggest hurdle was going to be immigration. I live in the US, and he was under the protection of Social Services in the UK. He’s in foster care in Britain.

Although it broke my heart to think that Alan might end up being lost to our family, I started seriously considering becoming a foster parent. If we had room in our home and hearts for Alan, certainly we had room for an American child in a similar position. Again, I asked my daughters what they thought. They’d already thought through the implications of a child, possibly neglected or abused, joining our family for a period of time and then, most likely, moving on. They were all for it, with one caveat.

We shouldn’t take in kids older than them. They wanted to be role models, or, as they put it “rome models.”

I was in complete agreement. I didn’t feel equipped to handle foster children any older than age 7. While I recognize the desperate need for foster care for older children, I just don’t think I’d be the right person for that. I’m good with younger children, and my experience with my daughters has given me experience on what is age-appropriate. The girls’ request to have kids their age or younger felt just right.

Let me make a confession. I also worried about the influence on my daughters of an older child who had been through the trauma of being pulled into foster care and all that led there. Fostering a younger child felt like a safer choice from the perspective of the forever children I already have. It feels ugly to admit that. I should be open to accept any child who needs me. I should be willing to take the risk. It’s not like I’m unaware of the enormous challenges any foster child, regardless of age, will have to overcome and will bring to the family.

Still, I know my limits. I can’t foster an older child, not at this point in my life and the lives of the twins. Sad as it is to say it, the science supports it.

In general, it seems, younger siblings tend to emulate the good or bad choices of their older siblings. Dr. Patricia East, of UC San Diego, found that younger sisters of women who became pregnant as teens were five time more likely than their peers to become pregnant as teens themselves. Five times more likely–and that’s taking into account similar socioeconomic circumstances between the two groups.

I’d rather my daughters be the good influence on a younger child in need than under the influence of an older one who has been through too much to bear. Selfish of me? Yes. But we parents have limits, and it’s wise to recognize them.

Are you willing to adopt a child of any age or do you have an age window in mind? Why?