One major issue facing children of many ba’alei t’shuva is lack of extended family who are part of their community. All their friends seem to have cousins being raised the same way they are, and these children do not. Their grandparents are not the same as those of their friends, and they do not have relatives’ simchos or family gatherings (of the same nature as their friends’) to attend. This can be very isolating for children, even if there are many siblings in the family, as extended family plays a crucial role in the frum community.
As the child of an FFB and a BT, I wanted to marry a BT, if only to give him and his future children the joy of being part of a large frum family, B”H. I am grateful that Hashem led me on that path.
It might be helpful to ba’alei t’shuva if a FFB family makes them feel like part of their own family. You don’t need to mentor them (unless they request specific advice), but you need to treat them like close family members. Well, maybe with more conscious effort since the blood bond isn’t there.