"kin altruism" that marks biological parents. Though it isn't essential -- many adoptive couples succeed wonderfully without it -- the evidence suggests that the biological tie between parent and child is important in securing the very stability so necessary for children to thrive.
Adoptive parents probably do not tell their adoptive children that they are adopted. The child would never know unless there is a significant genetic difference and even then it would take them some years to figure out unless told.
Homosexual couples are something different altogether. Homosexual behavior is abnormal to start with so how are they going to raise a child that is impossible for them to have out of choice biologically?
As the nation debates whether to institutionalize same-sex marriage, social scientists have been weighing in -- often with a heavy hand. As Mark Regnerus, author of a new study examining outcomes for children in a variety of home environments, notes social science regarding gay and lesbian parenting has swung from "presents challenges," to "no difference" to "superior" in the space of one decade. The American Psychological Association declared flatly in 2005 that, "Not a single study has found children of lesbian or gay parents to be disadvantaged in any significant respect relative to children of heterosexual parents." That prompted skepticism from...
Many adopted kids even have some degree of contact with their biological mother even -- which can be helpful in relieving the kids' worries that they must be somehow defective since their parents didn't want them.
Its not always the right course and can cause conflict, but since it results in women being more willing to put their inconvenient babies up for adoption rather than murder them in the womb the overall effect must be judged positive.