While certainly it is ‘ideal’ for a child to have both father and mother–in this world, things aren’t perfect. What about families where the mother–or the father–dies, or divorces, before the child is born? They don’t send the child back or take the child away.
In a situation especially where this is an older or a special needs child, certainly ‘one’ loving parent is preferable to ‘no’ parent. And who knows–maybe the single person will meet someone and marry? Can’t rule it out.
That’s my opinion. I really do not think that there is a canon law which forbids adoption by a single person; in fact, I believe there is at least one case of a priest who adopted an older child in the 1970s or 1980s as I seem to recall reading about it in the paper.
